Giant beaver becomes Minnesota’s official state fossil

The giant beaver is now Minnesota’s official state fossil.

Gov. Tim Walz signed the designation into law on May 23 as part of SF 3045, the State and Local Government omnibus bill. The provision marks the end of a years-long effort that began with an eighth-grade science assignment at Central Middle School in Eden Prairie.

State Sen. Steve Cwodzinski (DFL-49, Eden Prairie), a former teacher at Eden Prairie High School, carried the idea forward after students brought it to his attention around the time he was first elected.

The fossil, Castoroides ohioensis, was chosen through a Science Museum of Minnesota-led campaign involving over 11,000 Minnesotans and dozens of schools. A massive Ice Age rodent, the extinct beaver could grow up to seven feet long and weigh more than 200 pounds.

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Bill Prem, an Eden Prairie middle school science teacher, recalled that it started with a student asking if Minnesota had a state fossil. “We did some quick research and found out that we did not,” he said. That question eventually led to a classroom-wide research and advocacy project.

Students polled experts and invited the public to vote on finalists. Their top pick — the giant beaver — became the leading candidate, later championed by both the Science Museum and the Bell Museum.

In a statement made prior to the bill’s signing, Bell Museum Executive Director Holly Menninger said the fossil is one of the most popular exhibits among visitors. “We’re thrilled that Minnesota now has an official state fossil,” she wrote, anticipating the bill’s final approval. “This recognition celebrates our incredible natural history and the civic spirit that brought it to light.”

The law’s passage makes Minnesota the latest of more than 40 states to adopt an official fossil.