Geist is not an incorporated municipality, but rather a loosely defined area surrounding the Geist Reservoir. The Geist area is in high demand because of the waterfront property on the reservoir, and has become home to a number of local celebrities and expansive multi-million dollar homes.

Most of Geist's residential area falls within Lawrence Township in Indianapolis, which offers shopping at Castleton Square Mall, numerous other stores, restaurants and movie theatres. New Fort Harrison State Park is also in Lawrence Township, providing opportunities for hiking, fishing and other outdoor activities on 1,700 acres of beautiful preserved land.

Some of Geist's residential area also falls in Fall Creek Township, on the eastern side of Fishers. This part of Geist is served by Hamilton Southeastern Schools, while the Lawrence Township portion is served by Lawrence Township Schools. The population of this area is about the same as Carmel. Homes here start at about $100,000 and can range into the millions for waterfront properties.