ðɪ ɚɹˈɪdʒɪnəl ˌɛsˈeɪtʃ sˈɛvənti θɹˈiː wʌz dˈɛzɪɡnˌeɪɾᵻd ˌɔn ˈɔːɡəst twˈɛnti wˈʌn, nˈaɪntiːnhˈʌndɹɪd twˈɛnti θɹˈiː, fɹʌm ˈoʊldənbˌɜːɡ tə hjˈuːstən, ɐbsˈoːɹbɪŋ ðɪ ˈiːstɚn hˈæf ʌv ˌɛsˈeɪtʃ θɹˈiː ˈeɪ. ˌɔn ɑːktˈoʊbɚ twˈɛnti sˈɪks, nˈaɪntiːnhˈʌndɹɪd θˈɜːɾi tˈuː, ɪt wʌz ɹᵻɹˈaʊɾᵻd saʊθwˈɛst fɹʌm kˈeɪɾi tʊ ˈælɪtən, wɪððə pˈoːɹʃən fɹʌm ˈoʊldənbˌɜːɡ tʊ ˈɪndʌstɹi bˌiːɪŋ ɐnˈʌðɚ sˈɛkʃən ˌɛfˈɛm wˈʌnhˈʌndɹɪd nˈaɪn wʊd kənˈɛkt ðə tˈuː sˈɛkʃənz lˈeɪɾɚ.
The original SH 73 was designated on August 21, 1923, from Oldenburg to Houston, absorbing the eastern half of SH 3A. On October 26, 1932, it was rerouted southwest from Katy to Alleyton, with the portion from Oldenburg to Industry being another section (FM 109 would connect the two sections later).