The Archives has five original volumes of Sanborn Fire Insurance Survey Maps of Greensboro for the following years: 1902, 1907, 1913, and 1925 (one set with additions through 1933 and one updated through 1955/57).
The North Carolina Collection at UNC-Chapel Hill has digitized all of its Sanborn maps through 1922. Start by reading their introduction to Sanborn maps and their collection, or go directly to their Sanborn maps of Greensboro.
The only subsequent Sanborn map of Greensboro was originally published in 1925 and updated through the 1950s. An unaltered 1925 edition and one updated to 1950 can be accessed through NC LIVE, a collection of online databases available to North Carolina citizens through their local public libraries. Look for Digital Sanborn Maps (1867-1970) for North Carolina, and use your Greensboro or other North Carolina library card to login.