Founded in 1880 by clarinetist John Calhoun Deagan, J.C. Deagan, Inc. was a Chicago-based percussion manufacturer that played a foundational role in the development of mallet percussion in the United States. Originally based in St. Louis before relocating to Chicago in the early 20th century, the company produced glockenspiels, xylophones, marimbas, orchestra bells, organ chimes, aluminum chimes, Swiss handbells, the marimbaphone, tower chimes, tuning forks, and mallets. Deagan is credited with refining the marimba from a folk instrument into a concert-stage staple and with producing the first "scientifically tuned" glockenspiel.

The company is best known for inventing the modern vibraphone. In 1927, Deagan's chief engineer Henry Schluter developed the Model 145 "Vibraharp," which introduced aluminum bars in place of steel for a mellower tone, harmonic tuning to suppress dissonant overtones, and a foot-controlled damper bar — features that defined the vibraphone as it is known today. Vintage Deagan instruments, including the Vibraharp and various xylophone and marimba models, remain prized by collectors and percussionists.

The Deagan company was sold to the Slingerland Drum Company in 1977, then passed to the Sanlar Corporation in 1984, before the Deagan name and assets were acquired by Yamaha in 1986.

Deagan has 2 products cataloged on Equipboard, including Marimbas and Vibraphones. Their gear is featured by 2 artists, with the strongest followings in Rock and Jazz. Notable users include Eric Cannata and Paul Hoffert.