City Origins
Conroe Was Named for a Lumberman Who Built a Sawmill in 1881
The city of Conroe takes its name from Isaac Conroe, a Houston-based lumberman who established a sawmill on Stewarts Creek in 1881.
Isaac Conroe was born in the North and served as a Union cavalry officer. After the war he became a lumber businessman in Houston. In 1881 he built a sawmill on Stewarts Creek in what is now Montgomery County. The settlement that grew up around the mill was first called Conroe's Switch, named in honor of Isaac Conroe, with "Switch" denoting the railroad junction where the mill was located. The name was later shortened to Conroe.
By 1889, the town had grown large enough to become the county seat, replacing the town of Montgomery. Conroe was formally incorporated in 1904. Its spot at a railroad junction made it the natural business center for the surrounding region.
Source to confirm: TSHA Handbook — Conroe, TX