Along with Revell, AMT, and MPC, Monogram is sometimes called one of the traditional "Big 4" in plastic modeling.
The firm has been a premier maker of scale plastic models of aircraft, spacecraft, ships, cars, and military vehicles since the early 1950s and was formed by two former employees of Comet Kits. After thirteen years as a fully owned subsidiary of Hallmark Cards' Binney and Smith unit, Hobbico announced it was acquiring Revell-Monogram in 2007.
Founded in Chicago in 1945, the firm first made balsa wood model kits of ships and airplanes. Seaships such as the USS Missouri battleship, the USS Shangri-La carrier and the USS Hobby destroyer were among the very first products. Meanwhile, a company called Revell started making plastic kits in 1953, and Monogram responded with "All Plastic" "Plastikits" the first of which were a red plastic midget racer and a "Hot Rod" Model A. These two cars, and later an Indianapolis-style racer and hydroplane racing boat, were also offered with C02 "Jet Power". Early kits advertised that the models were made from "acetate parts molded to shape".
As the 1960s progressed, Monogram and Revell squared off as rivals in the scale model market. While companies like AMT and MPC focused almost exclusively on cars, Monogram and Revell were more diversified, offering aircraft, naval craft and other military vehicles.
When the company was bought by Mattel in 1968, custom vehicles designed by Daniel and others were seen in both small and large sizes in Hot Wheels diecast - and then in Monogram kit form. Examples seen in both Hot Wheels and Monogram venues were the Ice-T, the Red Baron, the Paddy Wagon, the S'cool Bus, the Sand Crab, and the T'rantula.
Source and more history: Monogram history.