State legislatures in the United States have the power to set boundaries for legislative districts. This is commonly done in response to the latest U.S. Census, which is done every 10 years. The first Census was done in 1790.

As the result of the Census, the number of seats that a state has in the House of Representatives might change, since apportionment of House seats is based on population and the maximum national total is 435. 

Population is also a driver at the state level, when legislators draw and redraw maps that encompass addresses of registered voters. The exact process of districting and redistricting varies by state. In some states, it is entirely up to state legislators how the district lines are drawn; in other states, it is common to hire an independent commission to draw up the district boundaries. In all cases, the maps must be approved by the state governor.

Most stage legislatures will have a majority belonging to one political party (and this is currently, in all cases, either the Democratic Party or the Republican Party). In practice, that means that the business of government in that legislature is usually run by the party holding the majority. Committee chairs commonly belong to the majority party, session agendas are set by the party's majority leader, and special projects like redistricting are run by the majority party.

State legislatures will meet in the year following a Census year to do redistricting. The new district boundaries will inform the election the following year. Elections for all of the House and one-third of the Senate occur every two years; presidential elections occur every four years.