As quoted from a website (http://www.kytravel.com/hist1.htm)
"This 14-room Federal-style home was the center of a 19th century hemp plantation. Designed from a plan by Thomas Jefferson and completed c. 1815, Farmington is furnished with antiques from the period. A summer kitchen, springhouse, stone barn and a replica of an early 19th century garden are located on the 18-acre grounds. The gift shop offers unusual Kentucky items. Open all year. House open Tues.-Sat. 10 a.m.-4:30 p.m., Sun. 1-4:30 p.m., last guided tour 3:45 p.m. Admission $6, seniors (60+) $5, students & children 6-18 $3, under 6 free."
Overall, the experiences of visiting this site and the history you are exposed to make this a worthwhile stop. Personally, the cheap look to some of the painting done in the mansion was difficult for me to overlook. For all the wealth that was required to own a home like this, I can't imagine anyone would have it looking the way it is currently being displayed.
