A Rocky Mountain bighorn sheep ewe keeps a close eye on her lamb in the rocks below Cheesman Dam, one of the dams that slows and captures water from the South Platte River for use as part of Denver's drinking-water supply. Cheesman Dam, which was named for Walter Scott Cheesman -- a Denver druggist, railroad builder, and designer of water infrastructure -- was the world’s tallest at 221 feet when it was completed in 1905. Cheesman was the first reservoir of Denver’s mountain storage facilities that helped expand Denver Water’s system. Built by immigrant stonemasons, the dam remains, after more than 100 years, the workhorse of the storage system and jewel among the Denver Water utility system's dams. Except for a small finger of the reservoir where fishers are allowed to try their luck, the dam and its vast reservoir are tightly secured and off-limits to human visitors, their boats and camping equipment, and their animals. Photo by Carol Highsmith, 2016.