sˈɪns ɪts ɪnˈɪʃəl kənstɹˈʌkʃən, ðɪ ˈoʊnli tˈuː tʃˈeɪndʒᵻz ɪnðə ɹˈaʊɾɪŋ wʌz ˌɔn dʒˈænjuːˌɛɹi twˈɛnti θɹˈiː, nˈaɪntiːnhˈʌndɹɪd sˈɛvənti fˈaɪv, wˌɛn ˌɛsˈeɪtʃ wˈʌnhˈʌndɹɪd wʌz ɛkstˈɛndᵻd ˈiːst zˈiəɹoʊ.fˈaɪv mˈaɪlz ɹᵻplˈeɪsɪŋ ðə sˈɛkʃən ʌv pˌiːˈɑːɹ wˈʌnhˈʌndɹɪd fɹʌm ɡˈoʊmɛz stɹˈiːt tə ðə wˈɛstɚn ˈɛnd ʌvðə kwˈiːn ˌɪseɪbˈɛlə kˈɔːzweɪ, ænd ðæt ˌɛsˈeɪtʃ wˈʌnhˈʌndɹɪd wʌz ɹᵻɹˈaʊɾᵻd ðə sˈɪɾi ʌv pˈoːɹt ˈɪzəbˌɛl, wˌɛɹ ðə ɹˈaʊt wʌz tɹænsfˈɜːd tə sˈɛpɚɹˌeɪt wˈʌn wˈeɪ sˈɜːfɪs stɹˈiːts tə bˈɛɾɚ hˈændəl flˈoʊ ˌɑːntʊ ðə kwˈiːn ˌɪseɪbˈɛlə kˈɔːzweɪ
Since its initial construction, the only two changes in the routing was on January 23, 1975, when SH 100 was extended east 0.5 miles replacing the  section of PR 100 from Gomez Street to the western end of the Queen Isabella Causeway, and that SH 100 was rerouted the city of Port Isabel, where the route was transferred to separate one way surface streets to better handle flow onto the Queen Isabella Causeway