Known for pioneering principles of regional planning, naturalistic systems approach to landscape architecture, and laying the groundwork for conservancies across the world.

Instrumental in the formation of The Trustees of Reservations, the world's first land trust, playing a central role in shaping the Boston Metropolitan Park System, designing a number of public and private landscapes, and wrote prolifically on a variety of topics.

While there, studying botany, geology, meteorology, marine life, ornithology, and entomology, Charles would write his parents later that fall recommending to look between Somes Sound and Seal Harbor if they wanted to build a house on Mount Desert Island: "Somewhere along that coast you will find a suitable spot, with beautiful views of the ocean, and hills, deep water anchorage, fine rocks and beach, and no flats."

In 1885, on Olmsted's advice, Eliot traveled to Europe to observe natural scenery as well as the landscape designs of Capability Brown, Humphry Repton, Joseph Paxton, and Prince Hermann von Pückler-Muskau.

In 1888 Charles married Mary Yale Pitkin from Philadelphia; this marriage produced four daughters: Ruth, Grace, Ellen, and Carola.

Her grandfather was Reverend Cyrus Yale who graduated from Williams College in 1811 and was a minister for 40 years at the Town Hill Church in New Hartford Connecticut.

The Yale, Pitkin, and Beadle Families would spend their summers at their farm called "Eaglesnest" on Town Hill Road in New Hartford Connecticut.

[16][17] On March 5, 1890, Eliot published an article entitled "Waverly Oaks" to defend a stand of virgin trees in Belmont, Massachusetts, in the process making a plea for preservation of the oaks and outlining a strategy for conserving other areas of scenic beauty in the same way that the Boston Public Library held books and the Museum of Fine Arts pictures.

This article resulted in a conference held at the Massachusetts Institute of Technology in 1890 on preservation of scenic beauty, and led to the enactment of Massachusetts legislation creating The Trustees of Reservations in 1891 — the world's first organization created to "acquire, hold, protect and administer, for the benefit of the public, beautiful and historical places."

"[citation needed] Over the next year, some 300 structures were cleared from on and around the beach, the train tracks were moved approximately 400 yards away from the water, a boulevard was put in place to separate buildings and houses from the sand, and a bandstand and pavilions were constructed.