Hi there, I'm guessing that you would be looking for US voices from the time you specified... but if it is in fact British/Irish/Commonwealth, or if you are merely interested, the British Library archive of accents and dialects is a great resource: http://sounds.bl.uk/Accents-and-dialects/Berliner-Lautarchiv-British-and-Commonwealth-recordings From the description of this section:

The Berliner Lautarchiv British & Commonwealth Recordings is a subset of an audio archive made between 1915 and 1938 by German sound pioneer, Wilhelm Doegen. Enlisting the support of > numerous academics, Doegen sought to capture the voices of famous people, and languages, music and songs from all over the > world. The collection acquired by the British Library in 2008 comprises 821 digital copies of shellac discs held at the Berliner Lautarchiv at the Humboldt Universität. It includes recordings of > British prisoners of war and colonial troops held in captivity on German soil between 1915 and 1918 and later recordings made by Doegen in Berlin and on field trips to Ireland and elsewhere. The content of the recordings varies and includes reading passages, word lists, speeches and recitals of songs and folk tales > in a variety of languages and dialects.

So many recordings are from 1915-18, with many of the contributors being born in the 1880s - teenagers in the period you are looking for, and indeed when they went to war.

Hope you find this interesting, if not useful!