FM 973 was first designated in Williamson County on November 23, 1948; its original routing was from  SH 95 north of Coupland to the Travis County line.
ˌɛfˈɛm nˈaɪnhˈʌndɹɪd sˈɛvənti θɹˈiː wʌz fˈɜːst dˈɛzɪɡnˌeɪɾᵻd ɪn wˈɪljəmsən kˈaʊnti ˌɔn noʊvˈɛmbɚ twˈɛnti θɹˈiː, nˈaɪntiːnhˈʌndɹɪd fˈoːɹɾi ˈeɪt; ɪts ɚɹˈɪdʒɪnəl ɹˈaʊɾɪŋ wʌz fɹʌm ˌɛsˈeɪtʃ nˈaɪnti fˈaɪv nˈɔːɹθ ʌv kˈʌplənd tə ðə tɹˈævɪs kˈaʊnti lˈaɪn.