Lock and Dam No. 20

Mississippi River Lock and Dam number 20
Location	Lima Township, Adams County, Illinois / Canton Township, Lewis County, Missouri, near Canton, Missouri
Coordinates	40°08′37″N 91°30′46″W / 40.14361°N 91.51278°W / 40.14361; -91.51278Coordinates: 40°08′37″N 91°30′46″W / 40.14361°N 91.51278°W / 40.14361; -91.51278
Construction began	1932 (1932)
Opening date	November 20, 1935 (1935-11-20)
Construction cost	US$4.45 million
Operator(s)	United States Army Corps of Engineers
Dam and spillways
Impounds	Upper Mississippi River
Length	2,369 feet (722 m)
Reservoir
Creates	Pool 20
Total capacity	58,000 acre·ft (0.072 km3)
Catchment area	134,300 sq mi (348,000 km2)
Lock and Dam No. 20 Historic District
U.S. National Register of Historic Places
U.S. Historic district
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Location	1⁄2 mi (800 m) N of Henderson St, Canton, Missouri
Area	83.9 acres (34.0 ha)
Built	1935
Architect	COE; Abbott, Edwin E.
MPS	Upper Mississippi River 9-Foot Navigation Project MPS
NRHP Reference #	04000180
Added to NRHP	March 10, 2004

Lock and Dam No. 20 is a lock and dam located on the Upper Mississippi River, about one mile upstream from Canton, Missouri.

The structure is located at river mile 343.1. It includes a 2,369 feet (722 m) long dam, 40 tainter gates, 3 roller gates, and a lock chamber that is 110 feet (34 m) wide by 600 feet (183 m) long. There is also an incomplete auxiliary lock. In 2004, the facility was listed in the National Register of Historic Places as Lock and Dam No. 20 Historic District, #04000180 covering 839 acres (340 ha), 1 building, 6 structures, 3 objects.

The Lock and Dam are on the site of the former town of Tully, Missouri. Tully was founded in 1834 and became a thriving river port and regional business hub until being virtually destroyed by major flooding in 1851. Left a crumbling "ghost town", what little that remained of Tully was finally removed during Lock and Dam No. 20's construction.