He served as a professor of early American history at a number of universities throughout the South and Southwest United States.

He mainly taught early American colonial history that concentrated on southern states, their notable figures, frontier life, the move westward, and how it impacted the social, economic and political fabric of colonial America and its transition into an independent nation.

His great-grandfather, Thomas Smith Abernethy, was a pioneer Methodist minister and one of the founders of the Alabama conference.

[1][3] Abernethy's work, The Formative period in Alabama, 1815–1828, published in 1922, was submitted as a doctoral dissertation to the faculty of Harvard University and was prepared under the direction of Professor Frederick Jackson Turner; the archives and manuscripts collected were made available by Thomas M. Owen, founder of the Alabama Department of Archives and History,[4][a] which made the depth of Abernethy's research possible.

[6] Upon completion of his graduate studies at Harvard, Abernethy began his career as a professor and historian of the southern colonies and states.

He was also honored by a Festschrift titled The Old Dominion; Essays for Thomas Perkins Abernethy, edited by Darrett B.