Over one hundred years ago, when hotel operator Myron O. Brown sought to build an exclusive resort community on Lake George in the Adirondacks, he looked for support from four Philadelphia millionaires who were summer residents of the area - E. Burgess Warren, William B. Bement, Robert Glendenning and George Burnham.

Together they bought Green Island for a hotel site and formed The Green Island Improvement Company. Later they were joined by investor John Boulton Simpson of New York City, who became the company's president.

The Sagamore opened in 1883 with luxurious and spacious accommodations that attracted a select, international clientele. Twice damaged by fire, in 1893 and 1914, The Sagamore was fully reconstructed in 1930 through the efforts of Dr. William G. Beckers of New York City, one of the hotel's early stockholders, and William H. Bixby, a St. Louis industrialist. Together they financed the cost in spite of the bleak economic climate of the period.

Throughout its history, The Sagamore has been a social center for the wealthy residents of Green Island and Millionaires Row, the stately mansions along the island's western shore. In 1954, the hotel hosted the National Governor's Conference, presided over by Vice President Richard M. Nixon, and hosted by Governor Thomas E. Dewey.