Over the next ten years, the McGraw-Hill Publishing Company continued to expand and prosper. Acquisitions included the Newton Falls Paper Co. in 1920 and the A.W. Shaw Co. in 1928. Additional offices were opened in England and California, and new products like Bus Transportation were introduced. James McGraw retired as President in 1928 and was replaced by Malcolm Muir, but remained as Chairman of the Board. McGraw-Hill stock was publicly traded for the first time in 1929, which was also the first year BusinessWeek was published.

James McGraw finally ended his long tenure with the company in 1935 when he stepped down as Chairman, though he retained the title of Honorary Chairman until his death in 1948. The family's involvement with the company continued, though, as he was succeeded by his son James McGraw, Jr. (Jay). Jay took over as President of the company two years later when Malcolm Muir retired. The 1930's and 1940's saw the continued development of McGraw-Hill, including the appearance of products in the aviation, health, and atomic energy fields. Jay McGraw retired from the Presidency and Chairmanship in 1950, and was replaced by his younger brother Curtis W. McGraw.

The 1950's brought tremendous expansion in all areas, particularly in the field of educational publishing. Since the original merging of the two book companies in 1909, McGraw-Hill had been steadily increasing its offerings in textbooks for college level students. Many of its offerings were, of course, connected to the traditional strengths of engineering and science, but by the mid-1930's McGraw-Hill had developed specialties in business, management, and social science textbooks. With the development of the post World War II baby boom the extension of these efforts into elementary and high school publishing was the natural next step. With the acquisitions of the Gregg company (a publisher of vocational textbooks) and the California Test Bureau (a developer of educational testing systems), the company established a presence in the K-12 area. McGraw-Hill also purchased the companies of Warren C. Platt, a petroleum-industry publisher in 1953, and the future looked promising. Curtis McGraw, however, died suddenly in September 1953, and his brother Donald C. McGraw had to take over as company President.