The Conococheague Aqueduct is a watered and fully operational aqueduct in Williamsport. It has three 60 -foot arches and is 196 feet long, making it the second longest aqueduct on the canal, behind the Monocacy Aqueduct. It began operation in 1835 and ended in 1924 when flooding damaged the aqueduct, along with other parts of the canal. Soon after, the Chesapeake & Ohio Canal Company closed the canal to boat traffic.

Restoration work on the aqueduct began in 2017 and was completed in 2019. The project involved strengthening the piers and supports, repairing the masonry, installing a period appropriate wall and iron railing, and making the aqueduct water-tight. Now visitors can take a free one hour interpretive boat ride led by the Park Service.

In 1861, Union troops destroyed the Conococheague Aqueduct to prevent Confederates from escaping through Williamsport after the battle of Antietam. Luckily, the solid construction of the canal works emerged intact. In 1863, Confederate soldiers damaged the aqueduct in an attempt to stop the Union’s transportation of coal, but it was repaired four days later. The berm wall collapsed several more times, though the most famous incident was when Frank Myers’ Boat No. 73 fell through  the wall of the aqueduct into the Conococheague Creek. Instead of repairing it, the Canal Company rebuilt it with wood.