Snagboats removed underwater trees, stumps, branches, and other debris that obstructed river navigation, using a grapple or clamshell to pull snags from the river and a scoop bucket to dredge silt from shallow areas, usually while working with barges and tug boats that carried away the debris. By the 1800s, the U.S. Army Corps of Engineers was responsible for most river improvement work, including locks, dams, diversion canals, flood control after the 1870s, and keeping rivers open for boat traffic. In 1829, Henry Shreve designed the first steam-powered snagboat, the Heliopolis, whose connected side-by-side hulls supported a derrick for lifting snags, and this double-hull design remained standard until the early 20th century. Built between 1925 and 1926 by the Charleston Dry Dock and Machine Company of Charleston, South Carolina, for the Montgomery District of the U.S. Army Corps of Engineers, the Montgomery was based in Montgomery, Alabama, and worked the Alabama-Coosa River system until 1933, when the district became part of the Mobile District and its home port shifted to Tuscaloosa, adding the Black Warrior-Tombigbee rivers to its duties. By the mid-20th century, Corps snagboats followed an annual cycle, conducting snagging operations from May through the end of the year during peak river traffic and spending January through May in dry dock for major repairs. In 1959, the Montgomery moved to Panama City, Florida, to work the Apalachicola, Chattahoochee, and Flint rivers, and its home port changed to White City, Florida, in 1979. Log books from the 1970s show daily operations included removing 120-170 snags per day. When the Corps of Engineers retired the Montgomery on 8 November 1982, it was the last sternwheel work boat operating on a southern river and one of two remaining steam-powered snagboats in the United States.