The area surrounding The Sagamore Resort is rich in history. As early as 1642 the land was explored by the French who named the lake "Lac Du Saint Sacrement" in honor of the Catholic sacrament of the Eucharist. Fighting among the French, British and native population occurred in the lake region during the French and Indian War, and is recorded by James Fennimore Cooper in The Last of The Mohicans. After the final British victory the lake was renamed for King George II.

Over a century ago, when hotel operator Myron O. Brown envisioned an exclusive resort community on Lake George in the Adirondacks, he recruited 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.

Opened in 1883, The Sagamore Resort featured luxurious and spacious accommodations that gained notoriety among a select, international clientele. In 1893 and 1914, the hotel was damaged by fire but 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 Resort has been a social center for the wealthy residents of Green Island and Millionaires Row, the stately mansions along the lake'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.

The hotel eventually fell into disrepair before closing its doors in 1981. In 1983, one hundred years after construction of the original hotel, builder and real estate developer Norman Wolgin, of Philadelphia, purchased the estate and restored it to its former grandeur. With Kennington Ltd., Inc. of Los Angeles, Wolgin formed a partnership under the name Green Island Associates to bring about this splendid restoration. The Sagamore was purchased in 2008 by Ocean Properties, LTD, who have since invested an additional $50 million in modern updates and renovations. The Sagamore Resort is listed in the National Register of Historic Places.

The Sagamore Resort, a member of Historic Hotels Worldwide since 2014, dates back to 1883.