The Parties in Congress, 1789–2027

Seat shares at the convening of each of the 119 Congresses, for every major party family and significant third party. Select an ideological dimension below to recolor the parties by their position on it in each era — opacity shows how salient the issue was to the party. Watch RACE to see anti-slavery politics pass from Free Soil and the anti-Nebraska Opposition into the Republican Party, and a century later cross the aisle.