We measure where and to what end parties take control of Congressional redistricting, which lets them redraw districts to favor their own candidates. We exploit the discontinuous change in a party's control of redistricting triggered when its share of seats in the state legislature exceeds 50 percent. Parties capture redistricting in states where they have suffered recent losses, which are temporarily reversed by redistricting. Opposition candidates are 11 percentage points less likely to win House elections just after redistricting. Consistent with recent Supreme Court rulings, African Americans are more likely to be segregated into overwhelmingly black districts under Republican redistricting.