1866 - B. P. Bartlett has a shop in the Mills Photograph rooms specializing in portraits made with oil paint

From Encyclopedia Dubuque:

“B.P. Bartlett. In 1866 Bartlett was the artist in Mills Photograph room. He specialized in portraits done in oils. The 1868-69 through 1873-74 Dubuque City Directory listed 128 Main. According to the 1878-79 through 1883 Dubuque Directory, this business was located at the northeast corner of 8th and Main.