Lock and Dam No. 15 is a lock and dam located on the Upper Mississippi River. It spans the river between Rock Island, Illinois and Davenport, Iowa. Lock and Dam 15 is the largest roller dam in the world, its dam is 1,203 feet (366.7 m) long and consists of nine 109 feet (33.2 m) non-submersible, non-overflow roller gates and two 109 feet (33.2 m) non-submersible overflow roller gates. It is unusual among the upper Mississippi River dams in that it has only roller gates, has different sizes and types of roller gates, it is not perpendicular to the flow of the river and is one of the few facilities that has a completed auxiliary lock. The main lock is 110 feet (33.5 m) wide by 600 feet (180 m) long and its auxiliary lock is 110 feet (34 m) wide by 360 feet (110 m) long.^[2] In 2004, the facility was listed in the National Register of Historic Places as Lock and Dam No. 15 Historic District, #04000175 covering 3,590 acres (1,450 ha), 2 buildings, 9 structures, and 1 object.

Lock and Dam No. 15
Lock and Dam No. 15 on the Mississippi River. View is from the Illinois side of the river looking across to Davenport, Iowa.
Location	Rock Island, Illinois / Davenport, Iowa
Coordinates	41°31′07″N 90°34′08″W / 41.51861°N 90.56889°W / 41.51861; -90.56889
Construction began	1931
Opening date	March 7, 1934
Operator(s)	U.S. Army Corps of Engineers, Rock Island District
Dam and spillways
Impounds	Upper Mississippi River
Length	1,203 feet (366.7 m)
Reservoir
Creates	Pool 15
Total capacity	100,000 acre⋅ft (0.12 km3)
Catchment area	88,500 sq mi (229,000 km2)
Lock and Dam No. 15 Historic District
U.S. National Register of Historic Places
U.S. Historic district
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Location	NW of Rodman Ave., Twd., NW tip Arsenal Island, Rock Island, Illinois
Area	359 acres (145 ha)
Built	1895
Architect	U.S. Army Corps of Engineers
Architectural style	Lock and Dam
MPS	Upper Mississippi River 9-Foot Navigation Project MPS
NRHP reference No.	04000175[1]
Added to NRHP	March 10, 2004