The keen eyes of the university archivists recognized man-made landmarks in these images, which then guided our research.
Zooming in on the image above revealed a structure with a distinctive architectural design. Enlarged (below) is the clock tower that overlooks Fort Sam Houston's Quadrangle, in San Antonio, Texas.
Construction of the United States Army post that would eventually become Fort Sam Houston began in 1876. The clock was installed in 1882. In 2005, "Fort Sam" became a part of Joint Base San Antonio, which incorporated Army, Navy, and Air Force operations in San Antonio, as well Army medicine operations. The clock tower still stands its post on the quadrangle as seen in the image to the right. The Texas State Historical Association has a brief history of Fort Sam and a postcard picture of the clock tower on their website, which was also used for comparison.
Identifying the clock tower at Fort Sam Houston is further evidence for locating this image in San Antonio Texas, but its installation date of 1882 does not help us narrow down our date range.