The Counties dataset was updated on October 31, 2023 from the United States Census Bureau (USCB) and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). This resource is a member of a series. The TIGER/Line shapefiles and related database files (.dbf) are an extract of selected geographic and cartographic information from the U.S. Census Bureau's Master Address File / Topologically Integrated Geographic Encoding and Referencing (MAF/TIGER) Database (MTDB). The MTDB represents a seamless national file with no overlaps or gaps between parts, however, each TIGER/Line shapefile is designed to stand alone as an independent data set, or they can be combined to cover the entire nation. The primary legal divisions of most states are termed counties. In Louisiana, these divisions are known as parishes. In Alaska, which has no counties, the equivalent entities are the organized boroughs, city and boroughs, municipalities, and for the unorganized area, census areas. The latter are delineated cooperatively for statistical purposes by the State of Alaska and the Census Bureau. In four states (Maryland, Missouri, Nevada, and Virginia), there are one or more incorporated places that are independent of any county organization and thus constitute primary divisions of their states. These incorporated places are known as independent cities and are treated as equivalent entities for purposes of data presentation. The District of Columbia and Guam have no primary divisions, and each area is considered an equivalent entity for purposes of data presentation. The Census Bureau treats the following entities as equivalents of counties for purposes of data presentation: Municipios in Puerto Rico, Districts and Islands in American Samoa, Municipalities in the Commonwealth of the Northern Mariana Islands, and Islands in the U.S. Virgin Islands. The entire area of the United States, Puerto Rico, and the Island Areas is covered by counties or equivalent entities. The boundaries for counties and equivalent entities are mostly as of January 1, 2023, as reported through the Census Bureau's Boundary and Annexation Survey (BAS).

The National Parks dataset is frequently updated by the National Park Service (NPS) and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). This dataset depicts National Park Service boundary data that was created by the Land Resources Division. NPS Director's Order #25 states: "Land status maps will be prepared to identify the ownership of the lands within the authorized boundaries of the park unit. These maps, showing ownership and acreage, are the 'official record' of the acreage of Federal and non-federal lands within the park boundaries. While these maps are the official record of the lands and acreage within the unit's authorized boundaries, they are not of survey quality and not intended to be used for survey purposes." As such this data is intended for use as a tool for GIS analysis. It is in no way intended for engineering or legal purposes. For the full data description, please go to https://irma.nps.gov/DataStore/Reference/Profile/2224545?lnv=True.

The National Highway System (NHS) dataset and its geometries was updated on May 01, 2024 from the Federal Highway Administration (FHWA) and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). The National Highway System consists of roadways important to the nation’s economy, defense, and mobility. The National Highway System (NHS) includes the following subsystems of roadways: Interstate - The Eisenhower Interstate System of highways, Other Principal Arterials - highways in rural and urban areas which provide access between an arterial and a major port, airport, public transportation facility, or other intermodal transportation facility, Strategic Highway Network (STRAHNET) - a network of highways which are important to the United States’ strategic defense policy and which provide defense access, continuity and emergency capabilities for defense purposes, Major Strategic Highway Network Connectors - highways which provide access between major military installations and highways which are part of the Strategic Highway Network, Intermodal Connectors - highways providing access between major intermodal facilities and the other four subsystems making up the National Highway System. A specific highway route may be on more than one subsystem.

The 2020 Adjusted Urban Areas dataset was compiled on December 31, 2020 from the Federal Highway Administration (FHWA) and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). The 2020 Federal Highway Administration (FHWA) Adjusted Urban Areas layer delineates the boundaries of adjusted urban areas as defined by the FHWA, based on the 2020 U.S. Census urban area boundaries. This nationwide geospatial dataset represents urbanized areas that have been modified through coordination between FHWA Division Offices, State Departments of Transportation (DOTs), and Metropolitan Planning Organizations (MPOs), in accordance with FHWA's Urban Area Boundary Adjustment guidelines. These boundaries are used for transportation planning and programming, eligibility determinations, and analysis purposes related to Federal-aid highway programs. A data dictionary, or other source of attribute information, is accessible at https://doi.org/10.21949/1528364

The National Network dataset is as of December 22, 2020 and is from the Bureau of Transportation Statistics (BTS) along with the Federal Highway Administration (FHWA), and part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). The National Network was authorized by the Surface Transportation Assistance Act of 1982 (P.L. 97-424) and specified in the U.S. Code of Federal Regulations (23 CFR 658) to require states to allow conventional combinations on "the Interstate System and those portions of the Federal-aid Primary System serving to link principal cities and densely developed portions of the states on high volume routes utilized extensively by large vehicles for interstate commerce which do not have any unusual characteristics causing current or anticipated safety problems. “The National Network (NN) includes almost all of the Interstate Highway System and other, specified non-Interstate highways. On March 31, 2025, four (4) records were updated to correct their "SIGNT1" and "SIGNN1" values. “The National Network (NN) includes almost all of the Interstate Highway System and other, specified non-Interstate highways. The network comprises more than 200,000 miles of highways. The National Network supports interstate commerce by regulating the size of trucks. This file is a geospatial representation of the National Network as described in 23 CFR 658 Appendix A and should not be interpreted as the official National Network and should not be used for truck size and weight enforcement purposes or for navigation. A data dictionary, or other source of attribute information, is accessible at https://doi.org/10.21949/1529045

The Federal Railroad Administration (FRA) Districts dataset was created on October 13, 2022 from the Federal Railroad Administration (FRA) and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). District boundaries represent geographic divisions of safety disciplines. These are no longer used to represent administrative boundaries.

The 119th Congressional Districts dataset reflects boundaries from January 03, 2025 from the United States Census Bureau (USCB), and the attributes are updated every Sunday from the United States House of Representatives and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). The TIGER/Line shapefiles and related database files (.dbf) are an extract of selected geographic and cartographic information from the U.S. Census Bureau's Master Address File / Topologically Integrated Geographic Encoding and Referencing (MAF/TIGER) Database (MTDB). The MTDB represents a seamless national file with no overlaps or gaps between parts, however, each TIGER/Line shapefile is designed to stand alone as an independent data set, or they can be combined to cover the entire nation. Information for each member of Congress is appended to the Census Congressional District shapefile using information from the Office of the Clerk, U.S. House of Representatives' website https://clerk.house.gov/xml/lists/MemberData.xml and its corresponding XML file. Congressional districts are the 435 areas from which people are elected to the U.S. House of Representatives. This dataset also includes 9 geographies for non-voting at large delegate districts, resident commissioner districts, and congressional districts that are not defined. After the apportionment of congressional seats among the states based on census population counts, each state is responsible for establishing congressional districts for the purpose of electing representatives. Each congressional district is to be as equal in population to all other congressional districts in a state as practicable. The 119th Congress is seated from January 3, 2025 through January 3, 2027. In Connecticut, Illinois, and New Hampshire, the Redistricting Data Program (RDP) participant did not define the CDs to cover all of the state or state equivalent area. In these areas with no CDs defined, the code "ZZ" has been assigned, which is treated as a single CD for purposes of data presentation. The TIGER/Line shapefiles for the District of Columbia, Puerto Rico, and the Island Areas (American Samoa, Guam, the Commonwealth of the Northern Mariana Islands, and the U.S. Virgin Islands) each contain a single record for the non-voting delegate district in these areas. The boundaries of all other congressional districts reflect information provided to the Census Bureau by the states by May 31, 2024. A data dictionary, or other source of attribute information, is accessible at https://doi.org/10.21949/1529006

The Time Zones dataset was compiled on October 04, 2019 and was updated January 05, 2023 from the Bureau of Transportation Statistics (BTS) and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). This layer is a digital representation of the geographic boundaries of the nine time zones that cover the United States and its territories (the Atlantic, Eastern, Central, Mountain, Pacific, Alaska, Hawaii–Aleutian, Samoa, and Chamorro time zones). The U.S. Department of Transportation (DOT) oversees the Nation's time zones and the uniform observance of Daylight-Saving Time. The oversight of time zones was assigned to DOT due to the importance of time coordination for transportation related activities. The time zones were established by the Standard Time Act of 1918 and amended by the Uniform Time Act of 1966. Time zones in the U.S. are defined in the U.S. Code, Title 15, Chapter 6, Subchapter IX - Standard Time. The time zone boundaries are defined in the Code of Federal Regulations (CFR), Title 49, Subtitle A, Part 71 - Standard Time Zone Boundaries. Segments used to compile the geospatial layer were derived from the CFR’s time zone descriptions (https://www.ecfr.gov/current/title-49/subtitle-A/part-71). Descriptions consist of segments referencing administrative boundaries, infrastructure, natural features, and geodesic lines. These segments are contained in various data layers in the National Geospatial Data Asset (NGDA) portfolio, the federal government’s authoritative geospatial data repository. Referenced segments were extracted from their NGDA and then merged to form continuous boundaries. In instances where there were multiple scales for a given dataset, the largest scale or most detailed layer was used. The standard time of the Atlantic zone is the Coordinated Universal Time (UTC) minus 4 hours; Eastern zone is UTC minus 5 hours; Central zone is UTC minus 6 hours; Mountain zone is UTC minus 7 hours; Pacific zone is UTC minus 8 hours; Alaska zone is UTC minus 9 hours; Hawaii–Aleutian zone is UTC minus 10 hours; Samoa zone is UTC minus 11 hours; and Chamorro zone is UTC plus 10 hours. For more information, please visit: https://doi.org/10.21949/1519143.

The Amtrak Routes dataset is as of January 05, 2024 from the Federal Railroad Administration (FRA) and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). This dataset is a single line representation of unique routes that are generated from the North American Railroad Network (Amtrak). It contains information on ownership, trackage rights, type, passenger, STRACNET, and geographic reference of the Amtrak system at 1:24,000 or better and the dataset covers all 50 states and the District of Columbia.

The Amtrak Stations dataset is as of September 23, 2024 from Amtrak and is part of the U.S. Department of Transportation (USDOT)/Bureau of Transportation Statistics (BTS) National Transportation Atlas Database (NTAD). This dataset contains Amtrak intercity railroad passenger terminals in the United States.