Shelby Davidson was born in Lexington, Kentucky, on May 10, 1868. He graduated from Howard University in 1893 with a Bachelor of Arts degree. Davidson went on to practice law, but is most remembered as an inventor.

Davidson journeyed to Washington, D.C. in 1887. Working in the auditing department of the United States Post Office, the young African-American became interested in finding a more efficient way to handle government auditing functions. In 1908, after studying adding machines for two years, Davidson found his answer in the form of his first invention: a rewind device for adding machines. Davidson was convinced his device would greatly improve efficiency by reducing both paper usage and the time clerks spent in paperwork. The government agreed with him and officially began utilizing the invention that same year.

Davidson was also keenly interested in mechanical tabulation and in 1911 patented a device designed to help postal clerks. This "automatic fee device," which Davidson continued to improve, paved the way for more efficient processing of postal fees.