Final answer:
The boundaries of congressional districts are usually redrawn every 10 years by state legislatures, following the U.S. Census to ensure equal voter representation, a process sometimes influenced by gerrymandering.
Step-by-step explanation:
Congressional district boundaries are usually redrawn every 10 years by the state legislature. This redrawing happens after population data is collected through the U.S. Census, so that each district can have a similar number of voters, ensuring even representation in the House of Representatives. The process of redrawing district lines to favor a specific political party is known as gerrymandering. In some cases, states use independent commissions to draw the lines, but primarily it's the state legislatures that perform this task.