A member of the Democratic Party, he was defeated for reelection in 2012 by 4th district incumbent Tom Latham, who decided to run against him after redistricting.

He later graduated from Artillery Officers Candidate School, eventually rising to the rank of lieutenant colonel.

During his military career, he earned two Distinguished Flying Crosses, two Bronze Stars, the Soldier's Medal, and various other awards and decorations.

In 1986, he ran for the United States House of Representatives, but was narrowly defeated by Scott Hughes of Council Bluffs in the Democratic primary.

In 2008 he supported passing the FISA bill granting telecommunications companies immunity from prosecution for their involvement in warrantless wiretapping of American citizens.

He voted for the final House version of the bill once he was convinced it provided adequate protection for telecom companies.

[10] During Boswell's 2010 re-election campaign, his views on gun rights and armed self-defense earned him an "A" rating from the NRA Political Victory Fund, which endorsed him over his (also "A"-rated) Republican rival.

The Iowa Independent reported that the conservative group Crossroads GPS criticized Boswell's vote approving the American Recovery and Reinvestment Act of 2009.

Law with ties to Karl Rove, had purchased $85,125 worth of TV time at KCCI, Des Moines local CBS channel targeting Boswell.

[14] Boswell won the Democratic nomination for the 3rd District after 12-year Republican incumbent Jim Ross Lightfoot made an unsuccessful run for the United States Senate.

He was likely helped by Bill Clinton carrying the district, as well as the endorsement of the normally Republican-leaning Iowa Farm Bureau.

Rumors circulated that Democrats were looking to replace him on the ballot for 2006's Congressional race against Iowa GOP Senate leader Jeff Lamberti, but Boswell's return to work and apparent good health put an end to the speculation.

He was a member of the board of directors for the Decatur County farmer's cooperative from 1979 to 1993, serving for most of that time as president.

At about 10:45 p.m. on July 16, an armed man came through the front door of Boswell's Iowa farmhouse, attacked his daughter, Cindy Brown, and demanded money.

[24] Boswell died in Des Moines, Iowa on August 17, 2018, after suffering from complications of pseudomyxoma peritonei, a rare form of cancer, for over 13 years.