Jane Jacobs was a famous urban theorist and activist born in Scranton, Pennsylvania, and she was renowned for her criticism of the most significant urban planning doctrines of her time. Even though Jacobs had no planning training, she changed how cities were perceived by publishing her book The Death and Life of Great American Cities in 1961. She disliked the centralized planning approach of Robert Moses, and instead, she promoted lively neighborhoods. Her observations were focused on sidewalks, parks, and the use of the space for both commercial and residential purposes as the critical components of a healthy urban environment.

In the mid-twentieth century, Jacobs became an activist against the massive urban renewal projects that aimed at erasing city districts to construct modern apartment houses and highways. Her activism prevented several of these projects, such as the Lower Manhattan Expressway that threatened to ruin areas such as Greenwich Village, SoHo, and Little Italy. Jacobs' work focused on appreciating cities as living entities that grow independently, not through top-down planning.

In 1968, Jacobs shifted to Toronto and remained an activist. She played a significant role in stopping the Spadina Expressway, which was to cut through downtown Toronto. Jacobs' philosophy of urbanism was not confined to North American cities alone but was adopted by planners and towns worldwide. She continued to write and think until she died in 2006, and her ideas about cities, urbanization, sustainability, and the city's capacity to promote creativity remain relevant to today's discourses.