Zipcar is an American membership-based car sharing company providing automobile reservations to its members, billable by the hour or day. Zipcar was founded in 2000 by Cambridge, Massachusetts residents Antje Danielson and Robin Chase, and is now led by Scott Griffith, Chairman and Chief Executive Officer. As of December 2010, the company offers a fleet of over 8,000 vehicles in urban areas throughout 28 North American states and provinces, as well as in the United Kingdom, and has over 560,000 members which the company refers to as "Zipsters". Zipcar offers more than 30 makes and models of self-service vehicles by the hour or day. Zipcar has major operations in Atlanta, Baltimore, Boston, Chicago, London, New York, Philadelphia, Pittsburgh, Portland, San Francisco, Seattle, Toronto, Washington D.C. and Vancouver. The company also has presence on over 230 college campuses.