Gayle Thornbrough (October 29, 1914 – November 8, 1999) was born in Hendricks County, Indiana, and grew up in Indianapolis. She joined the Indiana Historical Society in 1937 and served as its director of publications and library, an editor of historical documents, and its first executive secretary until her retirement in 1984. In addition to her work at the IHS, Thornbrough was involved in historical editing projects for the Indiana Historical Bureau from 1947 to 1966 and spent twenty months in 1967–1968 as a manuscript specialist at the Library of Congress in Washington, D.C. Thornbrough is best known for her contributions to editing historical documents. She is named as the editor of nearly twenty publications, the most notable include The Old Northwest: Pioneer Period, 1815–1840, a Puli