The White Rock Dam, completed in 1911 at a cost of $765,000, is what makes the lake (technically a reservoir) possible. Construction of the earthen dam, faced with concrete, began in early 1910. It was completed in mid-September 1911. Its core consists of 5,400 wood pilings driven 18 to 23 feet into the ground and covered with concrete. It is 40 feet high, 15 feet wide at the top, and 469.5 feet above sea level.
For many years a catwalk connected the top of the dam with the sidewalk that runs along Garland Road but it was removed. The spillway, where park visitors once played in the water, is now off-limits.