Plain guides to how U.S. congressional districts, Congress, and elections work. Start with the basics, then go deeper. To find your own district and representative, use the lookup on the home page.
The basics
Start here for what a congressional district is and who represents you.
- What Is a Congressional District?
- How Many Congressional Districts Are There?
- Congressional District Maps by State
- What Does a U.S. Representative Do?
- What Does a U.S. Senator Do?
- House vs Senate: What’s the Difference?
- What Is a Non-Voting Delegate?
Redistricting and gerrymandering
How district lines are drawn, and how the drawing can be used to favor one side.
- How Congressional Redistricting Works
- What Is Gerrymandering?
- Packing and Cracking
- Mid-Decade Redistricting Explained
- Redistricting vs Reapportionment
- What Is an At-Large Congressional District?
- How to Read a Congressional District Map
Elections and Congress
How Congress works and how elections are run.
- How a Bill Becomes Law
- What Is the Filibuster?
- Congressional Committees Explained
- How Long Is a Congressional Term, and When Are Elections?
- What Is a Swing District?
- What Is a Special Election?
- How to Find Your Congressional Representative
- How to Find Your U.S. Senators
- How to Register to Vote
- What Happens When a Congressional Seat Becomes Vacant
- How Special Elections to Congress Work
- How U.S. Senators Are Appointed to Fill Vacancies
- What Is a Runoff Election and Which States Use Them
Reference
Quick definitions of the terms used across these guides.
Tools
Look up and compare districts on this site.
- Find your district by address or ZIP
- Browse all 435 districts
- Compare two districts
- Districts by state
- 2026 Elections
Find and contact your representatives
How to Find What Is on Your Ballot: get a sample ballot for your address, see every race on it, and understand why two homes in one ZIP code vote on different contests.
ZIP Code to Congressional District Dataset: every US ZIP code and the districts it falls inside, as a free CSV, JSON file and open endpoint. 7,299 of 33,774 ZIP codes cross more than one district.