As an unincorporated community, Willis has no legally defined boundaries or population statistics of its own but does have its own post office with the 48191 ZIP Code.

[1] The community is located about 13 miles (21 km) southeast of Ann Arbor in the southeastern corner of Washtenaw County.

Willis owes its creation to the building of a Grand Trunk Railway line in 1880.

The Paint Creek post office was renamed Newcomb on September 27, 1881 and finally established as Willis on December 15, 1887.

[6] The line is currently operated by Norfolk Southern Railway but contains no station in the area.