On June 30, 1957, Donald Leinen was named the acting postmaster at the Onslow Post Office in Jones County in eastern Iowa. His confirmation as permanent postmaster was sent to the Senate by President Eisenhower, with an official title change coming July 24, 1958. That year, he purchased a lot from the town and built a modern post office building which he leased to the government. The facility featured 111 new lock boxes for patrons, plus the latest government equipment for handling and sorting mail. Leinen served as Postmaster through 1983; the post office continues to operate out of the building today.