Not a direct answer, but something that might help is to browse the National Archives.

Here is a collection of Documentary/Political recordings made by Thomas Edison between 1888 and 1927.

One that sticks out is Shackleton recounting his journey to the South Pole in 1908, which is the earliest recording I could find that fits your criteria.

Keep in mind that before magnetic tape became wildey available after WWII, audio recordings were really terrible methods of storing information. The methods they used were prone to degradation, couldn't record for very long times, and had awful fidelity. Most of the recordings you hear today from that era have been processed using advanced forensic audio techniques and have higher fidelity than the originals.