A Texas Garter Snake found in Olive Shapiro Park, Dallas, Texas.
Wikipedia has this to say about the Texas Garter Snake:
The Texas garter snake (Thamnophis sirtalis annectens) is a subspecies of the common garter snake (T. sirtalis) endemic to the United States.
It is found predominantly in central Texas, with disjunct populations in Kansas and South Dakota.
Texas garter snakes are a terrestrial species. They are uncommon, even in their central Texas range, and seldom found in large numbers. They can be found in a wide range of habitats, but are usually close to a water source. They have typically been found in stream-side vegetation or in damp soil near bodies of water.