ðə sˈɛkʃən ʌv ˌɛmˈɛn fˈɪftiːn bᵻtwˌiːn nˈuː ˈʌlm ænd ðɪ ˈaɪəwə stˈeɪt lˈaɪn wʌz ɚɹˈɪdʒɪnəli mˌɪnɪsˈoʊɾə kˌɑːnstɪtˈuːʃənəl ɹˈaʊt fˈɪftiːn, dˈeɪɾɪŋ bˈæk tə nˈaɪntiːnhˈʌndɹɪd twˈɛnti.
The section of MN 15 between New Ulm and the Iowa state line was originally Minnesota Constitutional Route 15, dating back to 1920.