She was the wife of Gifford Pinchot (1865–1946), the renowned conservationist and two-time Governor of the Commonwealth of Pennsylvania, and was also a close friend of U.S. President Theodore Roosevelt.

She played a key role in the improvement of Grey Towers, the Pinchot family estate in Milford, Pennsylvania, which was donated to the U.S. Forest Service in 1963 and then designated as a National Historic Landmark in 1966 A founding member of the Committee of 100 and major donor to the education and legal defense funds of the National Association for the Advancement of Colored People (NAACP) during the organization's first years of operation,[3] she has been described by historians at the Pennsylvania Historical and Museum Commission as “one of the most politically active first ladies in the history of Pennsylvania.”[4] Born into a wealthy, Victorian-era family in Newport, Rhode Island, in 1881, Cornelia Bryce was a daughter of Lloyd Stephens Bryce (1851–1917) and Edith (Cooper) Bryce (1854–1916), and a great-granddaughter of Peter Cooper, founder of Cooper Union, a science and engineering college in New York City which made its educational offerings available free of charge to every student admitted.

[10] According to historians at the Grey Towers National Historic Site, Cornelia Bryce's own political career was sparked by the women's suffrage movement—"a cause she supported vigorously.” In addition, she became an early financial supporter of the National Association for the Advancement of Colored People (NAACP), donating $120,000 to its education and defense fund,[11] “spoke out for birth control, women's rights and educational reform and blasted sweat shops and those who abused child labor in the work place,” and became a member of her “local school board, supported prohibition and was one of the first prominent women to take a ride in an airplane.” She also “encouraged women to take an active part in politics and career.”[10] On August 15, 1914, Cornelia Bryce wed Gifford Pinchot, the first chief of the U.S. Forest Service and a Progressive Party member she had met two years earlier during the “Bull Moose campaign,” an effort by former president Theodore Roosevelt to recruit candidates and other supporters to a third political party he was trying to form in the United States.

Realizing the 43-room fieldstone chateau and its surrounding 102 acres could be a hub for her family's conservation and political activities, she “made sweeping changes in the design and use of the home, making it ‘more fitting as a Governor’s home.’”[10] She oversaw the transformation of the home’s separate breakfast and dining rooms into a large sitting room and an expansion of the library, and worked with Chester Holmes Aldrich to beautify the estate’s grounds.

Despite this resistance, he instituted a pension program for blind Pennsylvanians, approved regulations to punish banks and corporations for misconduct, established the first environmental protection agency in America and a sanitary water board, launched a transportation initiative that upgraded 20,000 miles of rural roads, reduced utility rates, and repealed voting rights restrictions requiring Pennsylvanians to provide proof of residence by presenting copies of their tax receipts before voting.

An advocate for the reform of labor laws, improved educational opportunities for women, and the unionization of tradesmen, she ran for a seat in the U.S. Congress, but lost that Congressional election in 1926 and two others within a ten-year period (in 1928 and 1932).

[24][15] “If you are a woman and marry a Pinchot, or if you elect to buck the dominant political machine (and one follows the other as the night the day), you must expect to lose just so often—possibly half the time.

In 1929, she traveled with her husband “to the South Sea islands” as part of an eight-month expedition to study “bird and shell life,” and engage in “deep-sea diving, fishing for man-eating sharks and hiking over lava-encrusted volcanoes.”[25][5] Known today as the Pinchot South Sea Expedition, participants conducted zoological research and collected specimens on behalf of the U.S. National Museum of Natural History.

[27] Shortly after the United States entered World War II, Cornelia Pinchot began volunteering for the Office of Civilian Defense in Washington, D.C., and was appointed as the coordinator of the District of Columbia's food and housing services.

[10][31] Post-war, she traveled across Europe to study the difficulties European leaders were having in feeding and providing services for the large number of children and adults made homeless by the war.