Locks on the Chesapeake and Ohio Canal

The Locks on the Chesapeake and Ohio Canal, located in Maryland, West Virginia, and Washington, D.C. of the United States, were of three types: lift locks; river locks; and guard, or inlet, locks.

They were numbered 1 to 75, including two locks with fractional numbers (63+1⁄3 and 64+2⁄3) and none numbered 65. There is also the Tidewater Lock, sometimes called Lock 0, lock at the downstream end of the canal in Washington, D.C., where Rock Creek flows into the Potomac River.

The fractional numbering arose because locks 70–75 were completed in 1842, before locks 62 and 66. It was found that the level of the canal between locks 62 and 66 could be raised in three steps instead of four. So the additional locks through there were numbered 1+1⁄3 steps apart (62, 63+1⁄3, 64+2⁄3, and 66) so that the other locks, already completed, did not have to be renumbered.

While one source states that it takes about 10 minutes for a boat to lock through, experiments done in the 1830s show that it was possible for a boat to go through in 3 minutes on average and as fast as 2+1⁄2 minutes, while in 1897, it was shown that steamboats took 5 or 7 minutes to lock through going upstream or downstream (respectively).