Monticello was originally established as a 3,000-acre tobacco plantation by Jefferson's father, Peter, in the early 1740s. Jefferson changed the plantation's name from Shadwell to Monticello in 1770, but continued to grow tobacco as his main cash crop into the 1790s.  

Tobacco plants required very intensive labor and had a damaging effect on the soil. In the 1790s, Jefferson shifted away from growing tobacco and to growing wheat and grains. Monticello remained a primarily wheat plantation until Jefferson's death, but many other plants and livestock were raised for trade and consumption at Monticello.

Thomas Jefferson Quote

the greatest service which can be rendered any country is to add an useful plant to it’s culture

Thomas Jefferson’s Summary of Public Service
[after 2 Sep. 1800]