Joseph Baker Cowperthwait (October 15, 1833 - November 26, 1891) was an American book and map publisher. Born in Philadelphia, Cowperthwait became a successful map publisher, taking over the Samuel Augustus Mitchell Sr. (1792 - 1868) maps, atlases, and plates in 1850. His father, Hulings Cowperthwait (1802 -1873), began the publishing business, and was part of a few publishing firms, including Thomas, Cowperthwait, and Company and Cowperthwait, Desilver, and Butler. Cowperthwait, Desilver, and Butler dissolved in 1855 and H. Cowperthwait, Joseph B. Cowperthwait, D. M. Warren, George Pancoast, and Theodore H. Butler together formed H. Cowperthwait and Co. Cowperthwait died on Thanksgiving Day, 1891.