Miller-Main Dam, located in Afton, Iowa, is a privately owned earth dam completed in 1990 for the primary purposes of fire protection, stock, and small fish pond. Managed by the USDA NRCS, the dam stands at 27 feet high and spans 330 feet across Twelve Mile Creek. With a storage capacity of 18 acre-feet, the dam serves as a critical water resource for the surrounding area, particularly during times of drought.

Despite its low hazard potential and moderate risk assessment, Miller-Main Dam is regulated and permitted by the Iowa DNR, with regular inspections to ensure its structural integrity. The dam's uncontrolled spillway and soil foundation contribute to its efficient water management capabilities, while its location in Union County showcases the intersection of human intervention and natural resource conservation. For water resource and climate enthusiasts, Miller-Main Dam represents a harmonious blend of engineering ingenuity and environmental stewardship in the heart of Iowa's countryside.