Locks · Mississippi River
Chain of Rocks Lock 27: most tows wait, none wait long
Two in three tows waited more than an hour. The longest wait was 10.6 hours.
Chain of Rocks Lock and Dam 27 sits at mile 185.5 of the Mississippi River, at Granite City, Illinois. Between 4 September and 4 October 2026, 421 commercial tows locked through. The median one waited 86 minutes from arrival to the start of its lockage. That ranks 16th of the 173 locks with traffic in our archive.
A queue with a ceiling
66% of commercial tows waited more than an hour. One in ten waited longer than 3.6 hours. None waited twelve. The longest wait we recorded was 10.6 hours: the downbound Mark Shell, pushing 4 barges for Kirby Inland Marine, arrived on 10 September. Across all 421 commercial lockages, tows spent 774 hours waiting, about 32 days in total.
Small tows, hazardous cargo
The lock has two chambers. The larger is 1,200 by 110 feet, with a 21-foot lift. The median commercial tow pushed 5 barges and the largest pushed 15. 51% of commercial lockages carried a hazardous-cargo flag. Recreational and light boats made up 21% of all 533 lockages, an average of 17 lockages a day with a peak of 26 on 26 September.
| Operator | Lockages | Barges | Hours waited |
|---|---|---|---|
| Ingram Barge | 77 | 806 | 146 |
| Magnolia Marine Transport | 34 | 87 | 55 |
| American Commercial Barge Lines | 32 | 449 | 68 |
| American River Transportation | 32 | 416 | 56 |
| Kirby Inland Marine | 24 | 48 | 43 |
Ingram Barge averaged about 10 barges per lockage. Magnolia Marine Transport and Kirby Inland Marine averaged 2 to 3.
The last week went up
Weekly median waits held between 76 and 84 minutes for four weeks, then rose to 107 minutes in the week ending 4 October. Recent weeks usually read low, because a tow still waiting when we collected the data has no lockage yet and drops out of the count. The real figure for that week is likely higher.
At 10:06 UTC on 5 October the Corps reported two tows waiting and an average delay of 134 minutes over the previous four hours. Since live status began on 4 October, that delay has peaked at 187 minutes, with up to 9 tows waiting.
Mel Price Lock and Dam is the next lock upstream; our archive has no lock below this one. The live Chain of Rocks Lock page updates every 15 minutes.
Related
Sources: U.S. Army Corps of Engineers Lock Performance Monitoring System, archived by Lock Wait; chamber dimensions and opening year from the BTS National Transportation Atlas; operators from the USACE Waterborne Transportation Lines (2022) and FCC ship licences. Wait is measured from arrival to start of lockage. How every number is defined.