State legislative districts (SLD) are areas from which members are elected to state or equivalent entity legislatures. In most states, state legislative districts embody the upper (senate—SLDU) and lower (house—SLDL) chambers of the state legislatures. Nebraska has a unicameral legislature, and the District of Columbia has a single city council, both of which the Census Bureau treats as upper-chamber legislative areas for the purpose of data presentation. Therefore, there are no data for SLDLs in either Nebraska or the District of Columbia.

Every two years, the Census Bureau solicits changes to state legislative district boundaries from the states. Each state either verifies that there are no changes to their district boundaries or submits changes to be applied to the Census Bureau’s geographic database, along with a copy of the state law or applicable court order documenting the boundary. The Census Bureau then provides the states with a database extract for them to review and verify. This work is done through nonpartisan liaisons assigned to the Census Redistricting Data Program by the governor and legislative leadership in each state.