Baker v. Carr and One Person One Vote

By 1960, millions of Americans had moved from farms to cities, but many state legislatures still used district lines drawn decades earlier, some from the 1900s or 1910s. State legislators had little incentive to redraw lines that kept them in office, so rural districts stayed small while urban districts ballooned. In Tennessee, a rural district with a few thousand people and an urban district with ten or twenty times as many people each still elected just one state representative. That meant a rural voter's ballot counted for far more than a city voter's ballot in choosing who ran the state.

Before 1962, courts had treated redistricting as a political question, a dispute for legislatures and voters to settle, not judges. In Baker v. Carr, the Supreme Court changed that by ruling that malapportionment claims are justiciable: they involve manageable legal standards courts can apply, not just political judgment calls, so federal courts can hear them. That single move mattered more than any specific fix. It did not say how equal district populations must be or draw a new map for Tennessee. It just unlocked the courthouse door.

That gap is the hinge to what comes next. Because Baker v. Carr only established jurisdiction, later cases like Reynolds v. Sims and Wesberry v. Sanders had to supply the actual rule, that legislative and congressional districts must be roughly equal in population, the one person, one vote standard. Baker v. Carr is the key that opens the lock; the later cases describe what's behind the door.