A native of Virginia, in the years after the American Civil War Estill relocated with his family to east Texas where his father, Charles P. Estill, was a professor of language at Austin College in Huntsville, Texas A&M, and SHNI.

Estill was a member of the first graduating class of Sam Houston Normal Institute (1880) and later taught in Grimes County (1881). Upon the death of his father, Estill was named professor of Latin and English at SHNI. He served as vice president of SHNI beginning in 1898, and also taught at the State School of Methods in Austin (1888) and conducted summer normal institutes in Orange, Jewett, Sulphur Springs, and Huntsville between 1890 and 1908. Estill also authored early United States history texts for public-school students in southern states.

After serving as acting president during and following Henry Pritchett’s illness and death, Estill was named President of SHNI in August, 1908. As president he introduced new programs of study and extracurricular activities, promoted the creation of the Alcalde (1910) and Houstonian (1913), upgraded faculty numbers and preparations, and obtained professional academic accreditation for the school. In 1923 he oversaw the school’s transition into Sam Houston State Teachers College.

Estill helped appropriate funds for a new three-story library, which was named in his honor.

Upon his retirement he was honored with the title president emeritus and lived in a house north of campus. His death on February 12 came 40 years prior to the day of the fire that destroyed the Main Building. The Estill Window was one of many stained glass windows placed in the Memorial Hall of Old Main and dedicated April 21, 1955.

Estill and his wife, Loulie Estill, had five children, including daughter, Mary, who taught English at SHSTC and wrote the book Vision Realized about the school's history.