14,000 years ago, this would've been correct.

>WALRUS TUSK TURNS UP IN ORONO
>
>About 25,000 years ago when the state was covered during the ice age, the weight of the ice compressed the ground underneath. The ice receded about 14,000 years ago, and the ocean flooded the area up to what is now Medway.
>
>“The walruses would probably have been living on the ice margins the way they do now in the Arctic,” Jacobson said. “That walrus either died and ended up deposited there, or died on ice and ended up dropping into the water. It had to be an environment the walruses live in, and that would have been the only time [in what is now Maine].”
>
>Spiess agreed with Jacobson that walruses were in Maine as the ice age was waning.

Link.