Ten years later, on January 10, 1928, he became the fifth Secretary of the Smithsonian after the death of Charles Doolittle Walcott. Abbot would also maintain his position as Director of the Astrophysical Observatory. In 1927, Walcott had finalized the Smithsonian's strategic plan, which Abbot took on responsibility for upon his election as Secretary. The Smithsonian began a capital campaign in 1929, coinciding with the start of the Great Depression. During this tenure, Abbot oversaw the Smithsonian's participation in Works Progress Administration projects, including the Federal Art Project. Projects included new buildings and artwork at the National Zoo, and the start of the Smithsonian's first media project, a radio show called "The World is Yours". The program would be ceased in 1942 due to World War II. In the 1930s an expansion was approved for the National Museum of Natural History building, which would not begin until the 1960s. The Institute for Social Anthropology was also transferred to the Smithsonian during this time. While Secretary, Abbot would fail to acquire the National Gallery of Art for the Smithsonian. Abbot's role in the United States National Museum was also minimal, and was under the primary care of Assistant Secretary Alexander Wetmore.