The city is named after Northern-born Union Cavalry officer and Houston lumberman Isaac Conroe. Conroe founded a sawmill in the area 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.
In 1886, Conroe Mill School was established in the expanding town. Conroe Normal and Industrial College, a school for African Americans, served the area.
In 1922, a black man named Joe Winters was burned at the stake on the courthouse steps.
George W. Strake discovered the Conroe Oil Field in 1931. Distillate and natural gas were produced from the Cockfield Formation at a depth of about 5,000 feet (1,500 m). A second well in 1932 produced 1200 BOPD. By 1935, the field had produced 40 million barrels of oil.
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.