Lake Oswego is a city in the U.S. state of Oregon, primarily in Clackamas County, with small portions extending into neighboring Multnomah and Washington counties. Population in 2020 was 40,731, an 11.2% increase since 2010, making it the 11th most populous city in Oregon. Located about 7 mi south of Portland and surrounding the 405 acre Oswego Lake, the town was founded in 1847 and incorporated as Oswego in 1910. The city was the hub of Oregon's brief iron industry in the late 19th century, and is today a suburb of Portland.