Wallace is the founder, co-publisher, and co-editor of the Radical History Review and the author of Mickey Mouse History (1996), a collection of essays on American history. It includes an account of the "Battle of Enola Gay", detailing the feud over how to accurately represent the history of the dropping of the atomic bomb. He is working on a sequel to Gotham that will cover the history of New York City from 1898 through the Second World War.
Wallace was married with Carmen Boullosa, a leading Mexican poet, novelist, and playwright. He was previously married to Hope Cooke, the former Queen of Sikkim.
The Gotham Center for New York City History is a non-profit organization founded in 2000 by historian Wallace to "examine and explore the city's rich history, and to make it more accessible to citizens and scholars, teachers and students, locals and out-of-towners." It is part of the Graduate Center of the City University of New York (CUNY) and is located at 350 Fifth Avenue between 34th and 35th Streets in the Garment District of Manhattan, New York City. Wallace created the center in order to educate and entertain the public regarding the history of the city, using the talents of historians, scholars, preservationists, curators, librarians, teachers, filmmakers and amateur history buffs. Through its programs and its website, the center offers to the public free access to the historical resources necessary to study and appreciate the city's past and its future.