Omni Parker House (Massachusetts States) : The longest continuously operating hotel in the United States

Additions and alterations were made to the original building starting only five years after its opening. Between 1866 and 1925, the hotel increased in size with new stories and additions, eventually expanding its footprint over 41,400 square feet of land—the bulk of the city lot bordered by Tremont, School, and Bosworth Streets and Chapman Place. Founder Harvey D. Parker ran the hotel until his death in 1884, when the business passed on to his partners.

Subsequent proprietors of the Parker House were Edward O. Punchard and Joseph H. Beckman (1884–1891), Joseph Reed Whipple and the J. R. Whipple Corporation (1891–1933), Glenwood Sherrard (1933–1968), the Dunfey family (1968–1996), and Robert Rowling of TRT Holdings (1996–present). Omni Parker House, Boston, is a member of Historic Hotels of America, the official program of the National Trust for Historic Preservation. It is currently under study for becoming a Boston Landmark.

According to wikipedia