Data sources and processing
Census Boundary products are based on the 2020 census and are built from TomTom’s data product. Information about Combined Statistical Areas (CSAs) is sourced from OMB Bulletins.
Once extracted, block group, county, Minor Civil Division (MCD), place, and tract information is edited in a single database to ensure perfect overlay. When editing is complete, the different layers are separated into their respective products.
Note: The boundary portion of County Boundaries is also aligned with streets in Precisely’s StreetPro product.
Water features and shoreline boundaries
Census Boundary products include files both with and without shoreline representation. All states that border the Atlantic Ocean, Pacific Ocean, Gulf of Mexico, or the Great Lakes have two sets of boundary and centroid files for those areas that extend into water. One set of boundary files follows the shoreline and does not extend into water. A second set of shoreline buffer files extends into water out to a distance of 12 miles. Shoreline buffer files are available for the following states:
- Alabama
- Alaska
- American Samoa
- California
- Connecticut
- Delaware
- Florida
- Georgia
- Hawaii
- Illinois
- Indiana
- Louisiana
- Maine
- Maryland
- Massachusetts
- Michigan
- Minnesota
- Mississippi
- New Hampshire
- New Jersey
- New York
- North Carolina
- Northern Mariana Islands
- Ohio
- Oregon
- Pennsylvania
- Puerto Rico
- Rhode Island
- South Carolina
- Texas
- US Virgin Islands
- Virginia
- Washington
- Wisconsin
The coastal extreme is represented by the political boundary or 12-mile limit. Extensions into water are included in area calculations. Centroids are calculated with water buffers and may be placed in a water area.
Census Boundary products that are categorized as “without buffer” do not represent an exact 1-to-1 correspondence with the TIGER 2020 Census Roster. Some small islands that have no streets will not appear in the “without buffer” versions of these products.
Boundary files
In all file names listed in the following table, st represents the two-letter state abbreviation:
| File Type | File Name | Description |
| Block Group boundary files | blockgroup_b_st | Block Group boundary file with boundaries extending into coastal water |
| blockgroup_j_st | Block Group boundary file with coastal shoreline boundaries | |
| Census Block boundary files | block_b_st | Census Block boundary file with boundaries extending into coastal water |
| block_j_st | Census Block boundary file with coastal shoreline boundaries | |
| Census Tract boundary files | tract_b_st | Census Tract boundary file with boundaries extending into coastal water |
| tract_j_st | Census Tract boundary file with coastal shoreline boundaries | |
| County boundary files | county_b_st | County boundary file with boundaries extending into coastal water |
| county_j_st | County boundary file with coastal shoreline boundaries | |
| Minor Civil Division (MCD) boundary files | mcd_b_st | MCD boundary file with boundaries extending into coastal water |
| mcd_j_st | MCD boundary file with coastal shoreline boundaries | |
| Place boundary files | place_b_st | Place boundary file with boundaries extending into coastal water |
| place_j_st | Place boundary file with coastal shoreline boundaries |
Inventory files
Inventory files contain the point representations of objects listed in the associated boundary files. In all file names listed in the following table, st represents the two-letter state abbreviation:
| File Type | File Name | Description |
| Block Group boundary files | blockgroup_i_st | Block Group inventory file aligned with blockgroup_b_st |
| blockgroup_m_st | Block Group inventory file aligned with blockgroup_j_st | |
| Census Block boundary files | block_i_st | Census Block inventory file aligned with block_b_st |
| block_m_st | Census Block inventory file aligned with block_j_st | |
| Census Tract boundary files | tract_i_st | Census Tract inventory file aligned with tract_b_st |
| tract_m_st | Census Tract inventory file aligned with tract_j_st | |
| County boundary files | county_i_st | County inventory file aligned with county_b_st |
| county_m_st | County inventory file aligned with county_j_st | |
| Minor Civil Division (MCD) boundary files | mcd_i_st | MCD inventory file aligned with mcd_b_st |
| mcd_m_st | MCD inventory file aligned with mcd_j_st | |
| Place boundary files | place_i_st | Place inventory file aligned with place_b_st |
| place_m_st | Place inventory file aligned with place_j_st |