"John Hemmings was a carpenter. He was a first-rate workman, a very extra workman. He could make anything that was wanted in woodwork."
- Monticello overseer Edmund Bacon.

Jefferson established a Joiner's Shop on Mulberry Row to produce the distinctive architectural woodwork for his house. Here joiners (highly skilled carpenters) made doors, windows, and decorative finish work, such as cornices, mantels, balustrades, and railings. Beginning in the 1770s, Jefferson engaged a series of white joiners, including James Dinsmore and John Neilson, who trained slave apprentices. John Hemmings (1776-1833) succeeded Dinsmore as head joiner in 1809, making fine furniture for Jefferson, including cabinets, chairs, and tables.

Some of Hemmings’s woodworking signatures include: the way shelves are attached to the sides of a cupboard, the double-bead molding on shelves’ front edges, and the curved molding on door frames.

John Hemmings, who could read and write, often spelled his name with a double m, while other family members used a single m.