This correspondence (240 items; 1910-1924) consists primarily of letters written by President Harding (1865-1923), before and during his tenure as a U.S. senator, to his paramour Carrie Fulton Phillips (1873-1960), wife of a Marion, Ohio, store owner. Also included are drafts and notes for correspondence written by Phillips during her approximately fifteen-year relationship with Harding, as well as a handful of other related items.

This collection had been closed for fifty years as a result of court orders, settlement papers, and gift agreement. When the restriction expired on July 29, 2014, the Library digitized the originals and released the entire contents of the collection online . The correspondence file, which includes both final versions as well as some draft letters, is organized chronologically. By far, most of the letters were written by Harding to Phillips. Many of the letters are dated, but many others are either partially dated or not dated at all. Dates or approximate dates have been assigned to almost all of the undated letters and drafts. These assigned dates were based on the content of the letters, which reference known events or other dated letters. Sometimes both a bracketed date and a parenthetical date appear on the item and those dates may be years apart. The bracketed dates were written in 1963-1964 at the Ohio Historical Society, when the papers were temporarily located there. The parenthetical dates were created in 2014 when the papers were processed at the Library of Congress. Some letters are fragments with incomplete page numbering.

In addition to her name or common terms of endearment, Carrie Phillips is often addressed in the letters as "Sis." Harding uses a number of ways to sign his letters. WGH and "Gov" were used for public letters that might be read by others. "Constant," "Jerry," "JVH," and "FHK" indicate a letter that was intended for Carrie Phillips alone. In personal letters he sometimes uses the name "Pouterson" to refer to the two of them.

That Harding and Phillips had a romantic relationship dating from 1905 to at least 1920 is clear from these letters. Although the first letter in these papers dates from 1910, other letters refer to 1905 as the beginning of the relationship. The letters are at times deeply passionate, but there is more to the collection than love notes and sentimental poetry. The letters give travel and speaking engagement information on Harding. They wrote to each other when at least one of them was not in Marion, Ohio, and both of them traveled frequently. Intricate plans had to be made to meet or even to direct where the next letter should be sent. Harding often described his activities and colleagues.

After living in Germany for several years, Carrie Phillips was strongly pro-German both before and during World War I. She writes that it would be a betrayal of America to commit the nation to the interests of Britain. There are substantive exchanges in the letters and drafts concerning the war and Harding's role as a senator. Before U.S. entry in the war, Harding acknowledged in a letter to Phillips that he had constituents writing him in support of Germany. On March 25, 1917, he wrote, "How unthinking and unfair you are when you accuse me of playing politics! I represent a state with hundreds of thousands of German Republicans. Nobody knows better than I do that I seal my political fate by displeasing them." Even after the United States entered the war, Phillips, against the advice of Harding, publicly expressed her opinions about the war. In a letter of February 17, 1918, Harding, who as president would later commute the sentences of scores of political prisoners who had opposed the war, including Eugene V. Debs, tried to impress upon her the limits of free speech during the war: "I beg you, be prudent in talking to others. . . Remember your country is in war, and things are not normal, and toleration is not universal, and justice is not always discriminating." Before the Senate vote on the war resolution, there were oblique references in the correspondence regarding Carrie Phillips's power to expose Harding's marital infidelities. Regardless, he voted in favor of the resolution.

What Carrie Phillips wrote in her letters often has to be inferred from how Harding responds, however, there are some extended drafts by Phillips. See in particular drafts and notes from May, June, July 7, and Autumn of 1917, and March and December 5 of 1918. Phillips's notes and drafts reflect those times when she is most agitated, either over the war or concerning the perceived broken promises of Harding. The last letter in the collection exchanged between the two is dated July 20, 1920, although other items in the collection date to 1924.