Fillmore, IowaFillmore is an unincorporated community in Dubuque County, Iowa, United States. The community is located along U.S. Route 151, east-northeast of Cascade.HistoryFillmore's population was 30 in 1887, and was 115 in 1902. The population was 20 in 1940.EducationResidents are zoned to the Western Dubuque Community School District. They are assigned to Cascade Elementary School and Cascade Junior/Senior High School, both in Cascade.