The wild rats often seen in Chicago are Norway Rats (Rattus norvegicus). They are not actually Norwegian, but originated in Central Asia. In the 18th century they spread quickly across Europe, emigrated to our shores in 1775 just in time to become new Americans, and are now well established in most urban habitats in the northern U.S. and Canada. There may be as many as 235 million wild rats now living in the U.S.!

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