Street View of San Marcos
Identifying the location of the image above started by zooming in on the storefronts. We were able to read (from left to right) the words: Porter, Fish & Oysters, Lone ★ Bakery, and H.A. Nitzsche.
Examining San Marcos phone directories from the late 1800s through 1920s, we found those businesses listed. In addition, advertisements in newspapers found on the Portal to Texas History website from the same time range corroborated the names and locations of these businesses in San Marcos, Texas.
One business identified in the image was the Lone Star Bakery. An advertisement placed in the Texas Democrat, a San Marcos newspaper, dated October 1897 confirms the existence of the business.
Another business identified in the image was Porter. The name "Porter" is easy to read, but the first initials are not clear. Two possible results were identified. First, a T.A. Porter advertisement from The Texas Democrat, dated February 1898 confirms the existance of a T.A. Porter staples and fancy grocery store. Second, a J.R. Porter listing was found in a San Marcos telephone directory from 1899.
Since both the Lone Star Bakery and the T.A. Porter grocery advertisements indicate the businesses are on the south side of the square (or plaza), the data confirm the location of the photograph.
Based on this research, it is likely that this image is of San Antonio Street between Austin Street (now LBJ) and Guadalupe Street around 1900. While the time estimate is not specific, it does fit within the existing datapoints on the timeline.