The city is named after Northern-born Union Cavalry officer and Houston lumberman Isaac Conroe. Conroe founded a sawmill there in 1881. The city originally gained in wealth due to the lumber and oil industries. Originally named "Conroe's Switch", the area saw an influx of residents in the late 19th century due to the lumber demands on the piney wood forest of the area.
During the 1930s, because of oil profits, the city boasted more millionaires per capita than any other U.S. city, though only briefly. After the construction of Interstate 45, many Houstonians began to settle communities around Conroe.