Suckley was born December 20, 1891, at Wilderstein, the family home of Robert Bowne Suckley and Elizabeth Philips Montgomery in the Hudson Valley. She was the fourth of seven children, and a sixth cousin of Franklin D. Roosevelt. Generally called “Daisy” by those close to her, Suckley grew up at Wilderstein, where she was a neighbor of the future president. She attended Bryn Mawr College from 1912 until 1914, when her mother forbade her from finishing her degree. During World War I she served on Ellis Island as a nurse’s aide. Much of her family’s trade and shipping fortune was lost during the Great Depression, but she and Franklin Roosevelt remained close. In the early 1930s Suckley and Roosevelt spoke of having a cottage built at a shared favorite spot they called “Our Hill”, which eventually became Roosevelt’s Top Cottage. Two of the rare photographs of Franklin Delano Roosevelt in a wheelchair were taken by Suckley there.

Suckley raised Scottish terriers and gave one to President Roosevelt, which he renamed Fala. The dog quickly became famous, and Suckley wrote a children’s book about him.  During World War II, Suckley often stayed for long visits at the White House, keeping the president company. Although Roosevelt is known to have had an affair with Lucy Mercer during World War I, there is no direct evidence that he had a similar relationship with Suckley, although there was an emotional connection. Roosevelt apparently instructed Suckley to burn at least some of the letters he wrote to her, which has fueled speculation about their content. Surviving letters include affectionate personal remarks, as well as reports and reflections about the progress of the war and meetings with figures such as with Winston Churchill and Joseph Stalin at the Yalta Conference.  After Roosevelt died, his daughter Anna Roosevelt Halsted and a friend came upon a cache of Suckley’s letters, hidden in the box from his stamp collection that Roosevelt took everywhere with him. There is no indication, however, that his daughter read or understood the significance of the letters, which she returned to Suckley.

Having served as Roosevelt’s personal archivist, Suckley played a key role in setting up the Franklin D. Roosevelt Presidential Library and Museum in Hyde Park, where she worked until 1963.  In 1980 she helped establish Wilderstein Preservation Inc, a group dedicated to preserving the house and 45-acre riverfront property of her family home, now a National Historic Landmark. She continued to live at Wilderstein until her death.  Suckley died on June 29, 1991, in Rhinebeck, New York, at the age of 99.