J.F. Brennan Company

J.F. Brennan Company is a marine and heavy-civil contractor founded in 1919 and based in La Crosse, Wisconsin. The firm specializes in the water: dredging, dam and lock rehabilitation, pier and dock construction, and environmental remediation along rivers, harbors, and lakes across the country. Brennan works the kind of jobs that keep inland navigation moving, and in July 2026 the St. Louis Engineer District awarded the company a $43.6 million contract for site preparation and lock foundation work on the new 1,200-foot lock at Lock and Dam 25 on the Upper Mississippi. It’s a fourth-generation family business that has grown from regional river work into one of the larger inland-marine specialists in the U.S.

J.F. Brennan Company is a marine contractor that has worked in and along America’s inland waterways since 1919, when it was founded on the banks of the Mississippi River. The Brennan Brothers operation was reincorporated as J.F. Brennan Company in 1959, formally establishing La Crosse, Wisconsin as headquarters. More than a century on, the firm runs 22 locations across North America.

The work is squarely water-based and specialized. Brennan handles dam construction and repair, commercial diving, environmental remediation and dredging, aquatic habitat restoration, pier and dock construction, bridge work, and underwater concrete repair. That combination — heavy marine construction paired with an in-house dive team and environmental capability — is uncommon and lets the company take on complex projects on rivers, lakes, and reservoirs that general contractors can’t.

The firm’s contributions to river work have been recognized with an achievement award from the National Rivers Hall of Fame. For public agencies and owners with infrastructure on or under the water, Brennan offers a rare depth of waterways-specific experience built over more than 100 years.