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 ( and ) 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. p.20 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 steps apart (62, , , 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,Frequently Asked Questions , National Park Service 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 minutes, while in 1897, it was shown that steamboats took 5 or 7 minutes to lock through going upstream or downstream (respectively).
Guard locks Guard locks (inlet locks) regulated the water supply to the canal. At the slackwaters (particularly at Big Slackwater and Little Slackwater), they also allowed boats to reenter the canal from the slackwater. There is no guard lock #7, since Dam #7 that was proposed to be around mile 164 near the mouth of South Branch was never built. A steam pump was later put where this dam would have been in 1856.Unrau p. 208 footnote, 470 In 1872, a new steam pump was put 10 miles upstream at mile 174.2, and gave about 24 cubic feet per second of water. p. 215
The first guard lock was made of structures from George Washington's Potomac Company Little Falls skirting canal, and were repurposed for the C&O.Unrau p. 238
The second guard lock at Violette's lock, was confusingly numbered Lock 24 for a period of time when that was the end of the canal. Later, when the section up to Dam #3 (Harpers Ferry) was opened, Lock 24 was the lock at the Seneca Aqueduct (i.e. Riley's Lock). Guard lock #2 is also 88 feet 5 inches long, making it too small for a standard C & O canal boat (92 feet) to go through.Hahn, Towpath Guide, p. 51
LockMilesNameNearby landmarksCoordinatesDatePhoto15Guard Lock #1Consists of 2 gates: a feeder and guard gate. c. 1795222Guard Lock #2Violette's lock Nov 1830362Guard Lock #3Above Harpers FerrySept 1833485.4Guard Lock #4Big SlackwaterApr 18345106.8Guard Lock #5Little Slackwater Jan 18356134Guard Lock #6 Oct 18387164Not built8184.5Guard Lock #8End of Canal, Cumberland MDMay 1850
River locks
Three sets of river locks (not counting the guard locks) were used for traffic coming from Virginia.
The Goose Creek locks were 0.2 miles below Edwards Ferry (Lock 25), in section 51 used for traffic coming from Goose Creek on the Virginia shore. It allowed boats from the Goose Creek and Little River Navigation Company to enter. Only one Goose Creek boat was documented to enter the C&O canal, and there is no documentation of a C&O boat entering Goose Creek. The lock was eventually converted into a waste weir.Hahn, Towpath Guide p. 62-63 The Goose Creek lock is a staircase lock or combine lock:Hahn, Towpath Guide, p. 63. two locks with no intervening pound or basin, the upper gate of the lower lock being the same gate as the lower gate of the second lock. It was perhaps the only such lock on the C&O Canal.
The Shenendoah river locks (section 109), were across from Harper's Ferry, just below Lock 33 at the Shenandoah River. This lock let boats cross to Harpers Ferry with the mules walking on the railroad bridge, up the Shenandoah river, to the old Potomac Canal Bypass on the Shenandoah river by Virginius island. The railroad refused to let mules walk on the bridge, and from lack of business, the lock was abandoned. Stones from that lock were used for other purposes.Hahn, Towpath Guide p. 99-100
The Shepherdstown river lock (section 133) was served by a dam for Botler's mill on the Virginia Side. An 1889 flood destroyed the dam and the slackwater that necessitated the lock. It was later filled in and used for the towpath.Unrau p. 167, 238
Lift locks
The 74 lift locks came in several varieties. A boat traveling the length of the canal would also go through two guard locks: at Big Slackwater and Little Slackwater. p. 54-56
Locks were typically 100 feet long, 15 feet wide, and 16 feet deep. They lifted boats between 6 and 10 feet., p.68 Typical freight boats were 92 feet long, but the rudder could be turned to fit into the few shorter locks, such as Lock 28 (Point of Rocks), which was 90 feet, 9 inches.Hahn, Towpath Guide, p. 85 The only lock shorter than 90 feet was the troublesome Lock 36 at 89 feet, 11 inches, being the only lock less than 90 feet in length.
Locks were often whitewashed to make them easier to see at dawn or dusk.Kytle, p. 138
The locks were built on a foundation of 12 inch x 12 inch timbers, spaced about a foot apart, laid longitudinally below the walls, overlain by traverse timbers, also 12 inch x 12 inch. These in turn were overlain with 3-inch planks, with the masonry placed upon them. All timbers were intended to be permanently wet.Davies, p. xii
During construction, the builders left room on the berm side to allow another lock to be constructed alongside, but this never happened.Kytle, p. 73Hahn, Towpath Guide, p. 28
Debris that got into the lock sometimes had to be removed with a pitchfork.Kytle p. 138 If the paddle valve was stuck because of trash, the lock tender had a 20-foot pole with a hook to get the trash free.Kytle p. 206
Lock numbering changed over the years. Guard Lock No. 2 was numbered Lock 24 for a time, which could cause confusion with Riley's Lock, No 24, upstream. For a period of time in the early days, the locks were called by letters but that was later changed to numbers. Oddly enough, many of the lock numbers correspond to the contour elevatione.g., Lock 26 is at the 260-foot elevation line, and lock 30 is at the 300-foot mark, although it is doubted that things were planned that way, and many locks do not correspond to the elevation: e.g., Lock 72 is at the 580-foot mark.
Lock design
There were two designs used on the C&O Canal locks: the 1828 design and the 1830 design. Locks 1–27 (with the exception of lock 13) are to the older 1828 design, and locks 13 and 28–75 are of the 1830 design.
The 1828 design originally filled the lock chamber through the use of culverts in the lock masonry. The wicket, i.e. large paddle valve, hidden in the masonry recess where the upper gate fit in, would be opened, and water would flow through the lock masonry to three openings in the lock chamber. Both sides of the lock had these, so there would be a total of 2 wickets, and 6 openings. The upper gate is above the breast wall.Hahn, Towpath Guide, p. 47, 48nps.gov p. 71 Most of the wicket openings in the upper gate recess have been closed with masonry, but one wicket at Violettes Lock is still intact as of 2013 (see photo). Note that modern replacement gates in locks 1–23, have the wickets in the gates, since the original wickets in the lock masonry are inoperable. This system of routing water through the masonry was abandoned due to the tendency for debris to clog the opening.Hahn, Pathway, p. 186
The 1830 design eliminated the use of culverts in the masonry, and the upper gate is below the breast wall. The advantage here is that the lock can fill faster with the wickets being in the gate, but will not swamp a boat in the lock chamber. In the 1830 design locks, the upper and lower gates are both the same height. The majority of locks on the C&O canal are to this specification.
Having the wickets in the gates, particularly if the gates are above the breast wall, means that the water pouring in could swamp some boats in the lock. Filling the lock through culverts eliminated that problem, as well as putting the lock gate below the breast wall.
Lock 27 is a curious combination of the two specifications, having the culverts inside the masonry, but the upper gate below the breast wall. This is because of multiple contractors working on the lock after a lapse of time.Hahn, Towpath Guide, p. 75
Most locks were fitted with V gates, but some locks, particularly around Seven Locks (7, 9, 10, and 12), and also all three North Branch locks (Locks 73–75 Hahn, Towpath Guide, p. 216 ), were re-fitted with mechanical drop gates to speed up traffic in those areas. (Note that lock 6 had been converted to a drop gate, and later converted back to a V gate.Hahn, Towpath Guide, p. 26) With the mechanical locks, a lever pulls a rod which connects to a crank, connected to another rod which turned the wicket valve which was in the floor (below where the gate would rest when opened) and water flows below the floor and into the lock. Hahn states this brought the time to lock through from about 10 minutes to around 3 minutes.
Lock cramps
There were three different periods (or kinds) of iron cramps (like staples) to hold the lock stones together. First is inch x inches x 13 inches long, later inch x 2 inches x 13–14 inches long, and later, 1 inch round iron, and inch into the stone.Hahn, Towpath Guide p. 32
Double locks In 1875, the company decided to experiment with double boats (one boat tied to another, pulled by a team of mules) allowing them to decrease freight costs by 50%.Unrau p. 360Kytle, p. 73-74 The company extended 14 locks to do so. Locks 25 through 32 were extended for that reason. 11 locks were extended at the lower end (like Lock 25) and 3 were extended at the upper end, for a total of 14 extended locks on the canal. While since that time the stones from the downstream extensions have often been removed, the early mule rise (i.e. the towpath rise before the lock appears 120 feet earlier than normal) indicates the locks extended at the lower end.Hahn, Towpath Guide, p. 64 Lander Lock (No. 29) is a good example of this. While physical evidence shows that locks 25, 27, 29–33, 37, 38, 43, & 60 also were lengthened, Canal records only mention locks 5-7 being lengthened Unrau, Harland. Historic Structure Report, Historical Data, The Masonry Locks, Chesapeake and Ohio Canal National Historical Park, National Park Service, June, 1978
In May 1864, those who tended these double locks wanted higher pay for them, but were unsuccessful. As a result, one of the lockkeepers, S. C. Rogers, abandoned his post (Locks 45–46) in protest, and was replaced by Obadiah Barger.Unrau p. 800 Later in November 1864, Obadiah complained that he had been removed as locktender of the same locks (45–46) without just cause, and the locktender Susan Newcomer was never present but hired a youth without approval of the company, to tend the locks. After an investigation showed it to be true, she was sacked and Obadiah was reinstated as locktender again.Unrau p. 801
Lock tender's shanty
It was quite common to build a little shanty so that the lockkeeper could look for boats coming, especially during the night or inclement weather.
Increase in depth Some locks were increased in depth (Lock 25, 22, etc. for instance) by bolting timbers to the top of the lock. Some of those bolts are still in the stonework. This was apparently done because of silting in the canal necessitating raising the water level.Hahn p. 64
Bypass flumes
Most locks have a bypass flume, which allows water to bypass the lock to water the level below. If the flume was covered over with concrete, that generally meant that a roadway passed over the lock.Hahn, Towpath Guide p. 85 Originally the locks 1-27, with the possible exception of Lock 13 did not have bypass flumes, using the culverts to divert water, but later the bypass flumes were put in (which is what we see today).
Composite locks