The Baker v. Carr case established the "one man, one vote" doctrine. The United States Supreme Court heard the Baker v. Carr case in 1962. Before this Supreme Court decision, most legislative districts across Ohio and in many other states did not have similar population numbers. In Ohio, each county was entitled to have a legislator in the Ohio legislature before Baker v. Carr. In 1960, Franklin County had over 300,000 residents, while Vinton County had just eleven thousand people. Under the old system, each county received one legislator. Following Baker v. Carr, counties were not entitled to have a legislator. Now, states, including Ohio, were to create new legislative districts with approximately the same number of people in each one. The state legislatures were to fix the districts based on population.
As a result of Baker v. Carr, Ohio voters amended the state constitution in 1967. The amendment created a thirty-three-seat state Senate and a ninety-nine seat state House. The amendment also established that each senator and representative would have approximately the same number of constituents, as ordered by the United States Supreme Court.
Baker v. Carr and the amended Ohio Constitution was a direct result of urbanization. Throughout the first one-half of the twentieth century, many people left rural areas and moved to cities. The principal reason for this migration was declining opportunity in the countryside. Cities increasingly offered better paying jobs and more diverse employment opportunities. In Baker v. Carr, the United States Supreme Court attempted to correct the resulting problems in political representation.