Most of the brick and stonework on Monticello was done by local white masons, with some of the finer woodwork done by joiners from the mid-Atlantic region. That said, several foreign-born artisans are known to have worked on Monticello. Carpenter David Watson was British and his successor James Dinsmore and Dinsmore’s assistant John Neilson were Irish. They used already-skilled slaves, including John Hemmings, as their assistants. Lucia Stanton, a respected Monticello scholar, also notes a stonemason from Scotland. The window glass and mahogany sashes were European imports, but the rest of the materials were local as well.
Very few of the elements would have been completely unfamiliar to American architects and builders, and the classical orders were not among them. Peter Harrison, a British-born and trained gentleman architect, used Doric order in the 1747-9 Redwood Library in Newport, Rhode Island. The library is an example of the Palladian style popular in the mid-eighteenth century, which Neo-Classicism had much in common with.
Slightly predating the Monticello we know today was the Woodlands in Philadelphia (1788-9). Besides the Doric columns on the porch, the house also had oval-shaped rooms. This is an example of the Federalist Style, the most popular architectural style in the Early Republic, again using many familiar classical elements.
William Thornton’s 1792 design for the US Capitol features a dome that was quite Monticello-esque. Charles Bulfinch was also building a dome on the Massachusetts State Capitol at roughly the same time (1795-7).
If I have been unclear, my point is that many of the individual features of Monticello were fairly common among other high-style American buildings. The admiration for Monticello comes from Jefferson’s fusing together of various elements in the new style, influenced by his time in France, and the seamless inclusion more subtle details like chamfered corners and the recessed wall behind the portico. There are also the interior contraptions such as the seven-day Great Clock (originally made by Peter Spruck of Philadelphia) which are small marvels of their own.