U.S. Highway 169 was designated on October 23, 1930 to replace IA Highway 16.

U.S. Highway 169 extends 235 miles from the Minnesota state line south of Elmore, Minnesota, goes through Mount Ayr, and ends at the Missouri state line south of Redding, Ringgold County, Iowa, north of Grant City, Worth County, Missouri. The segment from the Union - Ringgold County line to Mount Ayr was paved in 1938. The last segment to be paved, in 1955, was completed from west of Mount Ayr at Highway 2 to the Missouri state line.

IA Highway 16 was designated on July 1, 1920, and decommissioned on October 23, 1930. It extended from the Minnesota state line south of Elmore, and ended at the Missouri state line northeast of Hopkins, Missouri. The segment between Mount Ayr and Redding were paved in 1930, present-day County Roads J-43 and P-32.

U.S. Highway 169 was re-routed around Delphos in either 1931 or 1932.

SOURCES:
http://en.wikipedia.org/wiki/U.S._Highway_169
http://iowahighways.home.mchsi.com/highways/us169.html