In the United States Supreme Court cases of Baker v. Carr (1962) and Reynolds v. Sims (1964), the court ruled that the principle of "one man, one vote" needed to be the basis of both houses of state legislatures, and that their districts had to be based on population rather than geographic counties.
ɪnðə juːnˈaɪɾᵻd stˈeɪts suːpɹˈiːm kˈoːɹt kˈeɪsᵻz ʌv bˈeɪkɚ vˈiː. kˈɑːɹ nˈaɪntiːnhˈʌndɹɪd sˈɪksti tˈuː ænd ɹˈɛnəldz vˈiː. sˈɪmz nˈaɪntiːnhˈʌndɹɪd sˈɪksti fˈoːɹ, ðə kˈoːɹt ɹˈuːld ðætðə pɹˈɪnsɪpəl ʌv "wˈʌn mˈæn, wˈʌn vˈoʊt" nˈiːdᵻd təbi ðə bˈeɪsɪs ʌv bˈoʊθ hˈaʊzᵻz ʌv stˈeɪt lˈɛdʒɪslətʃɚz, ænd ðæt ðɛɹ dˈɪstɹɪkts hædtə biː bˈeɪst ˌɔn pˌɑːpjʊlˈeɪʃən ɹˈæðɚ ðɐn dʒˌɪəɡɹˈæfɪk kˈaʊntiz.