 As Portland grew, it annexed St. Johns and expanded into the peninsula and other parts of the watershed. East of St. Johns, the Swift Meatpacking Company bought 3,400 acres (1,400 ha) in 1906 and established the community of Kenton. Other companies built packing plants and slaughterhouses along the slough, and by 1911 Portland had become the main livestock market for the Pacific Northwest. These and other early 20th century businesses, including stockyards, a dairy farm, a shingle company, and a lumber mill, flushed waste products into the slough. Starting in 1910, north Portland's residential sewage also poured into the slough through pipes laid for the purpose. In 1917, landowners along the slough had formed three drainage districts to control floods. They dug ditches, deepened existing water channels, and built levees to keep the rivers and the slough from flooding agricultural, industrial, and commercial property. Hoping to flush the slough with clean water from the river, city engineers created the crosscutting Peninsula Canal. The project largely failed because daily tides reversed the slough's flow and because both ends of the canal were at nearly the same elevation.
