Gaithersburg, Maryland – Gaithersburg is located in Montgomery County, 5 miles north of Rockville and 24 miles north of Washington DC., and covers over 9.5 square miles. Gaithersburg is home to a diverse and active community of over 52,000 residents. It is also home to the largest county fair on the East Coast, numerous spring and fall arts and craft fairs, an annual 4-H/FFA show, and an Olde Town Days festival.