Hall owned extensive properties in central Connecticut, as well as land inherited from his mother's prominent Rhode Island family, the Brentons.
The land-rich Halls and their kin were pillars of the Old Light faction of Congregationalists that opposed the Great Awakening and the ascendant commercial interests associated with it.
On graduating in 1786, he went to Philadelphia to attend medical lectures at Pennsylvania Hospital, then completed his training with Dr. Jared Potter of Wallingford (Yale 1760).
The marriage brought him substantial land holdings in Ohio, as well as a host of distinguished relatives, including brothers-in-law, Stephen Titus Hosmer, who would become Chief Justice of the State of Connecticut, Enoch Parsons, who would head the Middletown branch of the Bank of the United States, and Samuel Holden Parsons, who would long serve as High Sheriff of Middlesex County.
He was particularly concerned with epidemic disease, repeatedly petitioning town authorities in Wallingford and Middletown for permission to establish a "pock house" for inoculating against small pox.
In 1796, Hall played a heroic role during a yellow fever epidemic at Knowles Landing, south of Middletown on the Connecticut River.
He was noted as an educator of physicians and often had as many as six apprentices residing with him in his spacious house on Middletown's Main Street (William Brenton Hall Account Book, 1807–1809).
Had Hall followed his Yale classmate and fellow physician Elihu Hubbard Smith to New York City—where political and religious heterodoxy was tolerated—he might have had a more distinguished career.