Lock 27


Locks 27 moves more cargo than any other navigation structure on the Mississippi River. The structure is situated near the southern end of the 8.4-mile long, man-made Chain of Rocks Canal. After 1940, only a single impediment prevent the maintenance of a safe and reliable 9-foot navigation channel on the Mississippi River from St. Paul, Minn., to New Orleans. This impediment, known as the Chain of Rocks Reach, was a 17 mile series of rock ledges that began just north of St. Louis and was extremely difficult and dangerous to navigate.

The canal was designed to allow vessels to bypass the treacherous reach. To ensure adequate depths in the pool below the old Lock and Dam 26, a non-moveable, low water dam was constructed across the river, near the old Chain of Rocks bridge. This dam is known as Dam No. 27 and the Chain of Rocks Dam.

Vital Statistics

Location: Granite City, Ill.
Mississippi River Mile: 185.5
1st Day of Operation: February 7, 1953
Average lift: 15 feet
Pool size: 13,000 acres
Pool length: 27.8miles
Lock characteristics (Main Chamber):
1,200 feet long
110 feet wide
Lock characteristics (Auxiliary Chamber):
600 feet long
110 feet wide
Dam Characteristics:
2,500-foot long non-movable
low-water dam
Phone number: (618) 452-7107
Marine Radio: 12

Nine-Foot Navigation Channel

Located in Granite City, Illinois, Lock and Dam 27 is part of the Upper Mississippi River Nine Foot Navigation Project. The Project, authorized by the Rivers and Harbors Act of 1930, created and ensured a nine-foot deep navigation river channel.

Located in Granite City, Illinois, Lock and Dam 27 is part of the Upper Mississippi River Nine Foot Navigation Project. The Project, authorized by the Rivers and Harbors Act of 1930, created and ensured a nine-foot deep navigation river channel.

Located in Granite City, Illinois, Lock and Dam 27 is part of the Upper Mississippi River Nine Foot Navigation Project. The Project, authorized by the Rivers and Harbors Act of 1930, created and ensured a nine-foot deep navigation river channel.

The Chain of Rocks Canal

In 1940 the Chain of Rocks Reach was the only obstacle that prevented the success of the nine-foot navigation project. This 17 mile stretch of the river was rife with rock ledges that rendered it naturally unnavigable. The Corps built the 8.4 mile long Chain of Rocks Canal to bypass this portion of the River.

Locking Process

The lock chambers consist of 2 miter gates, one vertical lift gate, and four valves (two at each end). All boats wishing to pass through a dam must lock through the lock chamber, even during open river conditions when there is only a 10 or 12 inch difference between the upper and lower pools. Lockage is completed by using a system of valves to raise and lower the water level in the lock chamber. The filling valves are opened to allow water to enter the chamber, making it the same height as the upper pool, and the emptying valves are opened to allow water to drain out, making the chamber the same height as the lower pool. There are two sets of valves, the filling valves (located at the upper pool) and the emptying valves (located at the lower pool). During the process, no pumps are used, the chamber is operated solely on gravity. This is an elevator system for boats. Raising and lowering the water adjusts the boat to the necessary pool level. Without the locks the boats would face a drop of as much as 20 ft.

Annual Tonnage

Year Tonnage Lockages
2009 60,534,314 8,132
2008 58,218,139 7,500
2007 67,714,832 8,681
2006 73,361,655 8,650
2005 68,369,897 7,945
2004 71,169,714
8,321
2003
77,466,308
9,133
2002
83,825,396
9,299
2001
81,090,628
9,199
2000
82,633,959
9,124
1999
83,378,714
9,215
1998
80,746,809
8,967
1997
77,168,006
8,860
1996
79,440,582
9,814
1995
84,423,520
9,387
1994
77,328,058
9,403
1993
67,796,856
7,935
1992
81,463,112
10,706
1991
81,233,688
10,954
1990
85,373,942
11,990
1989
75,352,256
11,561
1988
79,224,302
11,753
1987
78,091,375
11,754
1986
68,362,269
10,390
1985
65,137,963
9,368
1984
76,762,335
11,912
1983
80,844,273
12,411
1982
75,203,822
11,330
1981
76,001,136
12,441
1980
76,394,103
12,608
1979
67,969,250
Na
1978 68,357,137 12,100
1977 64,265,100 10,818
1976 64,541,662 12,577
1975 58,189,032 8,526
1974 56,575,494 8,693
1973
54,416,133
8,634
1972
56,768,448
10,571
1971 48,705,045 11,912
1970 50,747,918 11,353
1969 46,379,053 11,003
1968 43,072,743 11,196
1967
43,243,645
11,135
1966
39,821,625
10,257
1965
35,926,212
8,884
1964
32,611,483
9,408
1963
29,916,257
8,941
1962
28,461,788
9,266
1961
24,714,762
8,676
1960
22,942,101
7,785
1959
22,142,370
7,369
1958
20,358,104
6,423
1957
17,756,706
6,124
1956
16,050,793
6,270
1955
14,783,744
5,452
1954
12,508,052
4,459
1953
8,127,305
3,386