Prospect No. 1 is a historic earth dam located along Little Sandy Creek in Sublette, Wyoming. Built in 1914 for irrigation purposes, this dam stands at a height of 20 feet and has a storage capacity of 957 acre-feet. Despite its age, the dam has a low hazard potential and is currently in poor condition, as assessed during its last inspection in 2017. Despite its condition, the dam continues to serve its primary purpose efficiently, while also providing fire protection, stock watering, and small fish pond support to the local area.

The dam's spillway type is uncontrolled, with a width of 10 feet, and it has an outlet gate in the form of a slide (sluice gate). The maximum discharge capacity of the dam is 390 cubic feet per second, ensuring effective water management during peak flow periods. While the dam's risk assessment is moderate, with a rating of 3, there is a need for ongoing maintenance and potential rehabilitation to ensure its long-term stability and safety. Overall, Prospect No. 1 remains a vital water resource infrastructure in Sublette County, Wyoming, contributing to the region's agricultural and ecological sustainability.