Cosmopolitan began as a family magazine, launched in 1886 by Schlicht & Field as The Cosmopolitan.

Paul Schlicht told his first-issue readers that his publication was a "first-class family magazine", adding, "There will be a department devoted exclusively to the interests of women, with articles on fashions, on household decoration, on cooking, and the care and management of children, etc., also a department for the younger members of the family."

Cosmopolitan's circulation reached 25,000 that year, but by March, 1888, Schlicht & Field were no longer in business. John Brisben Walker acquired the magazine in 1889, and E. D. Walker, formerly with Harper's Monthly, took over as the new editor, introducing color illustrations, serials and book reviews. It became a leading market for fiction, featuring such authors as Annie Besant, Ambrose Bierce, Theodore Dreiser, Rudyard Kipling, Jack London, Willa Cather and Edith Wharton. The magazine's circulation climbed to 75,000 by 1892.

In 1897 Cosmopolitan announced plans for a free correspondence school: "No charge of any kind will be made to the student. All expenses for the present will be borne by the Cosmopolitan. No conditions, except a pledge of a given number of hours of study." When 20,000 immediately signed up, Walker could not fund the school and students were then asked to contribute 20 dollars a year. Also in 1897, H. G. Wells' The War of the Worlds was serialized, as was his The First Men in the Moon (1900). Olive Schreiner contributed a lengthy article about the Boer War.

In 1905 William Randolph Hearst purchased the magazine for $400,000 (approximately $11,000,000 in 2007 prices) and brought in journalist Charles Edward Russell, who contributed a series of investigative articles, including "The Growth of Caste in America" (March, 1907), "At the Throat of the Republic" (December, 1907 - March, 1908) and "What Are You Going to Do About It?" (July, 1910 - January, 1911) and "Colorado - New Tricks in an Old Game" (December 1910).

Other contributors during this period included Alfred Henry Lewis, Sinclair Lewis, A. J. Cronin, David Graham Phillips, George Bernard Shaw, Upton Sinclair and Ida Tarbell. Illustrators included Francis Attwood, Dean Cornwell, James Montgomery Flagg and Harrison Fisher.

With a circulation of 1,700,000 in the 1930s, Cosmopolitan had an advertising income of $5,000,000. Emphasizing fiction in the 1940s, it was subtitled The Four-Book Magazine since the first section had one novelette, six or eight short stories, two serials, six to eight articles and eight or nine special features, while the other three sections featured two novels and a digest of current non-fiction books. During World War II, sales peaked at 2,000,000.

The magazine began to run less fiction during the 1950s. Circulation dropped to slightly over a million by 1955, a time when magazines were overshadowed during the rise of paperbacks and television. The Golden Age of magazines came to an end as mass market, general interest publications gave way to special interest magazines targeting specialized audiences.

Helen Gurley Brown arrives

Cosmopolitan's circulation continued to decline for another decade until Helen Gurley Brown became chief editor in 1965 and remodeled the magazine as New Cosmopolitan. After countless denials by other publications, Brown finally landed an opportunity to put a unique perspective on a tiresome magazine meant for both men and women.Benjamin, Jennifer. "How Cosmo Changed the World." Cosmopolitan 2009: n. pag. Web. 28 Sep 2009. . The magazine was renamed Cosmopolitan in 1967. In the early 1970s, Cosmopolitan became a women's magazine. The magazine eventually adopted a cover format consisting of a usually young female model typically in a low cut dress or bikini. The magazine focused on young women and published articles that openly talked about sexual issues.

Her uproar of a magazine was not her first publication dealing with sexually liberating woman. In fact, she first wrote a book in 1962, Sex and the Single Girl, which instantly became a best seller. Identical to her magazine Cosmopolitan, this novel focused on a sexually fearless single lady who dates many men. Fan mail begging for Brown’s advice on many subjects concerning women’s behaviorisms, sexual encounters, health, and beauty flooded her front door after this book released. Brown sent the message to the books fans stating how a woman should have men complement her life; not take it over. Enjoying sex without shame was also an empowering message she incorporated in both publications.Gianoulis, Tina. "Cosmopolitan." Bowling, Beatniks, and Bell-Bottoms: Pop Culture of 20th-Century America. Ed. Sara Pendergast and Tom Pendergast. Vol. 4: 1960s-1970s. Detroit: UXL, 2002. 867-868. Gale Virtual Reference Library. Gale. University of Northern Colorado. 28 Sept. 2009 ]. In conjunction with the campaign, Cosmo's editor-in-chief, Kate White, approached Congresswoman Carolyn Maloney (D-NY), known for her support of women's health issues, with concerns that women weren't fully aware of the dangers of indoor tanning and the effectiveness of the current warning labels. After careful review, the Congresswoman agreed that it was necessary to recommend that the FDA take a closer look. She and Representative Ginny Brown-Waite (R-FL) introduced the Tanning Accountability and Notification Act (TAN Act - H.R. 4767) on February 16, 2006. President Bush signed the act in September 2007, and the new federal law requires the FDA to scrutinize the warning labels on tanning beds and issue a report by September 2008. American Academy Of Dermatology Association Commends President Bush For Signing Tanning Accountability And Notification (TAN) Act

In its January 1988 issue, Cosmopolitan ran a feature claiming that women had almost no reason to worry about contracting HIV long after the best available medical science indicated otherwise. The piece claimed that unprotected sex with an HIV-positive man did not put women at risk of infection, and went on to state that "most heterosexuals are not at risk" and that it was impossible to transmit HIV in the missionary position. This article angered many knowledgeable people including AIDS and gay rights activists.

Cosmopolitan, as well as other women's-interest magazines, have been criticized for using published psychological research studies to gain credibility for their articles on sex and relationship advice but vastly misrepresenting or misconstruing data and findings from these studies in order to appear more "shocking", "newsworthy", and "more relevant to popular culture".