He studied or "read the law" with David McCloud and was admitted to the bar in South Carolina in 1829.

He was called the "John Marshall of Texas" for the role he played in the development of Texan law from the republic's early years, "laying the foundation of its judiciary system".

[1][2] The challenges were far beyond the law; Hemphill became known for an incident in which he fought Indian warriors who had attacked him in a courtroom while his court was in session.

He was subsequently chosen as a Texas delegate to the Provisional Confederate Congress, a position he held until his death in Richmond, Virginia.

He arranged for their education, sending them in the late 1850s to the newly founded Wilberforce College in Ohio, considered a "training ground" for abolitionists before the Civil War.