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.
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.