That is not likely to have an accurate answer. Sepia photographs are still taken (or created in photo editing software) to the present day. Originally, sepia was used extensively as it preserved b&w photos in way that was the most stable of all toned images.
That being said, 1900-1940s sepia images were quite popular. In fact the opening and closing sequences of The Wizard of Oz were sepia toned. Even recently, a few movies of the 70s-90s were also sepia toned (for the effect).
Starting around the late-40s, quite accurate color photos were available for the average photographer, and, as such, sepia were less prevalent but still done. The need to for preserving B&W images became less essential ass the demand for B&W decreased as color images took the forefront.