Founded in 1837, DeKalb remained a small community until the arrival of the Chicago and Northwestern Railroad in 1853. DeKalb received its charter in 1856. DeKalb's central location brought easier shipping of crops and access to larger markets.
Agriculture was the primary economic activity until the 1873-1874 when farmer Joseph Glidden developed barbed wire and began commercial mass production of his new invention. Glidden sold half of his interest to hardware merchant Isaac L. Ellwood and together the two formed the Barb Fence Company. Two months after Glidden filed his application for a patent, lumber salesman Jacob Haish also applied for a patent and on June 25, 1874, ran interference papers against Glidden's patent. After 18 years of legal wrangling, Glidden's patent was declared the "Winner". The industry gave DeKalb a place in history and the nickname "Barb City".
In 1865 H. B. Gurler moved to DeKalb, and later attempted to create high-grade milk. Gurler began shipping his "Pure Milk" to Chicago in 1895. The founding of Northern Illinois State Normal School in 1895 added education to Dekalb's landscape. Agriculture again came to the forefront with the creation of the DeKalb County Farm Bureau in 1912, the first organization of its kind. In the 1930s, the DeKalb AgResearch Corporation marketed its first hybrid seed corn.