Highland #1, also known as Mulligan, is a privately owned dam located in Weld County, Colorado, near the city of Platteville. Built in 1879, this earth dam stands at a height of 17 feet and has a storage capacity of 1382 acre-feet for irrigation purposes. Situated on the St. Vrain Creek, Highland #1 has a spillway width of 80 feet and a significant hazard potential, although its condition assessment as of December 2020 is deemed satisfactory.

Managed by the Colorado Department of Water Resources, Highland #1 undergoes regular inspections and is subject to state regulations, permitting, and enforcement. With a moderate risk assessment rating, the dam poses a potential risk that is being actively managed by authorities. Despite being over a century old, this historic structure continues to serve its intended purpose effectively, storing water for irrigation while contributing to the local hydrological landscape. For water resource and climate enthusiasts, Highland #1 offers a fascinating glimpse into the intersection of infrastructure, water management, and environmental stewardship in the American West.