Lock and Dam No. 3, Navigation lock and embankment dam on the Mississippi River near Red Wing and Diamond Bluff, Minnesota, United States.

This dual-purpose facility combines a lock system that enables vessels to navigate between different water levels with an earth-filled embankment dam that regulates river flow and maintains navigable depths along the Mississippi River corridor.

Construction of Lock and Dam No. 3 was completed in 1938 as part of a comprehensive federal navigation improvement project designed to transform the upper Mississippi River into a reliable commercial waterway for inland shipping.

The structure represents the intersection of industrial engineering and regional commerce, serving as a symbol of early 20th-century American infrastructure development that shaped the economic and social fabric of southeastern Minnesota communities.

The facility operates under the supervision of the U.S. Army Corps of Engineers, providing essential services for commercial barge traffic while offering visitor viewing areas and educational opportunities for the public to observe hydraulic engineering operations.

Unlike many modern concrete dams, this embankment structure utilizes locally sourced soil and rock materials compacted into layers, creating an economical yet durable barrier that has successfully managed Mississippi River conditions for over eight decades.