The Slingerland Banjo Company was established in Chicago around 1915 by Henry Heanon.
By the 1920s they were manufacturing a wide range of instruments including banjos, banjo-mandolins, banjo-ukuleles, guitars and mandolins, under the "May-Bell" label, from premises at 1815 Orchard Street, Chicago, Illinois.
The company later changed its name to the Slingerland Banjo and Drum Company and subsequently, in the 1930's, to the Slingerland Musical Instrument Manufacturing Company.
The Slingerland name is currently owned by Gibson.
Pictures of MayBell courtesy of Intermountain Guitar & Banjo
Pictures of banjo-uke courtesy of John Kay