[2][3] Bertram, descended from the New York Dutch Schoonmaker political family,[3] was employed as an agent of the Standard Oil Company and worked extensively abroad.

[2] In 1941, the family moved to the Dutch-Caribbean island of Aruba,[2][4] where Schoonmaker's father continued to work for Standard Oil and her mother ran nursery schools.

[5] Schoonmaker was primarily raised in Aruba, in a community she described as "a colony of expatriates from over the world";[5] she also spent part of her childhood in Portugal.

[8] Schoonmaker was interested in a career in international diplomacy and began attending Cornell University in 1957, where she studied political science and the Russian language.

While taking a graduate course in primitive art at Columbia University, Schoonmaker saw an advertisement in The New York Times that offered training as an assistant film editor.

The job entailed assisting an "editor" who was randomly cutting frames from classic European films (such as those by Truffaut, Godard and Fellini), so that their length would conform to the running times of U.S. television broadcasts.

[4] She signed up for a brief six-week course in filmmaking at New York University, where she came into contact with young Martin Scorsese, who was struggling to complete his short film What's a Nice Girl Like You Doing in a Place Like This?.

[14] Schoonmaker received her first major screen credits when she and Scorsese both became part of the editing team on Michael Wadleigh's seminal music festival documentary, 1970's Woodstock.

[16] Her use of superimpositions and freeze frames brought the performances in the film to life and added to the movie's broad appeal, thus helping to raise the artistry and visibility of documentary film-making to a new level.

Schoonmaker equaled the record for the most Oscar wins (three) in the Best Film Editing category, shared with Ralph Dawson, Daniel Mandell, and Michael Kahn.

[25] In 2012, on the 75th anniversary of its founding, the Motion Picture Editors Guild issued a list of the 75 best-edited films of all time based on a survey of its membership.

[26] Only George Tomasini, the editor of Alfred Hitchcock's films in the 1950s and 1960s, has more appearances on this list, with four; and only Dede Allen also edited three pictures, each from a separate decade, hers particularly from the 1960s through the 1980s.