After graduating from high school and then secretarial school in Scranton in 1933, Jacobs worked for a year as a reporter for The Scranton Tribune. She then moved to New York, where she worked for four years at a variety of jobs and freelance newspaper and magazine writing before embarking on a self-directed program of university study. More intent on pursuing diverse interests than on obtaining a degree, Jacobs chose courses selected from the general studies program at Columbia University rather than complete the more conventional degree-granting program at Barnard College. In 1940 Columbia University Press published Jacobs's book Constitutional Chaff, a compilation of rejected suggestions for the US Constitution.
In 1940 Jacobs became an editorial assistant and then a writer for the trade magazine Iron Age (later New Steel). In 1942 she became a pamphlet writer for the Office of War Information, and subsequently a pamphlet and magazine writer for the US State Department of Information. In 1952, when that office relocated to Washington from New York, she became an associate editor for Architectural Forum magazine.
As a citizen activist in the 1960s, Jacobs received credit for helping to save West Greenwich Village and Soho from demolition for urban renewal and highway construction. A grant from the Rockefeller Foundation enabled her to write her acclaimed book The Death and Life of Great American Cities, which was published in 1961 after a two-year leave of absence from Architectural Forum.
In 1968, during the Vietnam War, Jacobs left the United States with her husband and children and settled in Toronto, where she immediately became involved in a fight to stop expressway expansion (see "STOP SPADINA!"). Through community activism she continued to make a mark on her chosen home, promoting healthy neighbourhoods and lobbying for conditions that encourage eclectic economic enterprise. In the fall of 1997, during a month-long, Toronto-based celebration of her work and thought sponsored by urbanist and philanthropist Alan Broadbent, Jacobs surprised her listeners by proposing the possibility that Toronto separate from Ontario, a proposal consistent with her view that the cultural and economic vitality of cities should be matched by increased political power. In the spring of 2001 she helped initiate and was a key participant in a meeting of the mayors of five Canadian cities convened to discuss ways of altering the balance of power in favour of LOCAL GOVERNMENTS.
Since 1961, when The Death and Life of Great American Cities was an instant hit with the general public despite neglect by the planning establishment, until her death Jacobs continued to probe into the workings of societies in several books about how cities and their economies work. Her ability to observe and then codify behaviour and occurrences had the effect of making complex ideas readily accessible. Her occupation and preoccupation with the local, with things that work smartly and directly, is combined with an appreciation for the delicate complexity of all systems and a search for patterns of relationships within them. Non-linear thinking and the application of the ecological paradigm to human endeavour as well as to natural phenomena characterized her approach.
Although dismissed by some for her matter-of-fact logic and her rejection of grand academic theories, Jacobs attracted a diverse following of urban thinkers and civic practitioners. She was known outside North America primarily as an economist, pattern observer and analyst of complex systems. Her books are frequently included on reading lists for post-secondary courses in disciplines including architecture, complexity science, ecology, economics and urban planning.
A reluctant celebrity who preferred her typewriter to the limelight, Jacobs spurned numerous offers of honorary degrees from universities around the world because she rejected honorifics and was suspicious of "credentialism." In June 1998 she was invested as an Officer of the Order of Canada. In 2000 she was awarded the Order of Ontario. Also in 2000 she received the Vincent Scully Prize in Architecture awarded by the National Building Museum, Washington.
Her husband, Robert Jacobs, died in 1996. Together they had three children, James, Edward and Burgin.