William W. McGaa (17 April 1824 – 15 December 1867) was a 19th‑century mountain man and an early participant in the settlement of what later became Denver, Colorado. Born in Scotland, he emigrated to the United States and, during the Colorado Gold Rush, lived among the Arapaho under the alias “Jack Jones.”
McGaa is noted for his involvement with William Larimer, Jr., in the 1858–1859 establishment of St. Charles (the predecessor of Denver). He purportedly claimed to be the son of the Lord Mayor of London and asserted ownership of a Scottish family estate named Glenarm—claims that have not been independently verified.
In exchange for assistance from local Native American groups, McGaa allegedly facilitated the transfer of land along Cherry Creek to the new settlement, asserting authority through his alleged marriages to Arapaho women. As part of this arrangement he is credited with naming several Denver streets after his native wives—Wazee and Wewatta Streets—as well as “Champa,” purportedly derived from a Sioux word for “cherry.” He also named Glenarm Street (after his claimed family estate) and McGaa Street, which was later renamed Holladay Street and ultimately Market Street.
Contemporary accounts describe McGaa as a troublesome figure; he was reputed to be heavy‑drinking and to overpromise on behalf of the settlement’s founders. He died in Denver at age 43. His son, William Denver McGaa, is recorded as one of the first children of mixed European–Native ancestry born in the city (8 March 1859).
Sources: Wikipedia article “William McGaa”; historical accounts from Denver Public Library and contemporary newspaper obituaries.