The story
The firm was started in 1866 by Charles F. Curtis and W.G. Hemingway; they had been engaged in the grocery business for a short time in Clinton, Iowa. They bought out the Claussen and Thornburg interests in the firm of Claussen, Thornburg & Smith, a small sash and door factory. (The original firm was known as Curtis, Hemingway & Co.)
In 1867 George M. Curtis bought out the company holding of Mr. Smith, and in 1868 Charles F. Curtis and George M. Curtis bought out Hemmingway's interest.
In the fall of 1868 Judson E. Carpenter, who was an uncle of Charles F. and George M., came to Clinton, Iowa, from Rochelle, Illinois, and invested with them, and the firm name, adopted at that time, was Curtis Bros. & Co. Their business at that time was the manufacturing of sash, doors, blinds, mouldings, stair work and everything pertaining to that class of manufacturing.
From Wikipedia’s article on Curtis Bros. & Co, shared under CC BY-SA 4.0.3