An American Tail: The Treasure of Manhattan Island (1998)

"Meet Fievel. In his search to find his family, he discovered America."

Fievel and his friend Tony Toponi find a map that they believe points to a treasure buried somewhere beneath Old New York, and the plucky rodent is determined to find it. However, what he discovers under the city is a tribe of Native American mice who were driven underground by prejudiced European immigrants.