This collection documents Adam Badeau's career as Grant's secretary during the war, as well as a diplomat and Grant's biographer after it. Researchers interested in the particulars of Badeau's career should consult the Ulysses S. Grant Association newsletter in folder 69 in order to establish details of the beginning of his career, his rise in the military administration, and his relationship with Grant.

Badeau's letters offer a lot of insight into the military events he experienced. He met regularly not only with Grant, but with William Tecumseh Sherman, Horace Porter, Richard Busteed, George Henry Thomas, Orville Babcock, Ely Parker, John Rawlins, and others. His relationships with these individuals are described in his correspondence with James Harrison Wilson, which comprises most of this collection. There's also some interesting information on Edwin Booth, brother of John Wilkes, who is considered by some to be the greatest American actor of all time. In these letters, Badeau provides some meaningful commentary on these figures as well as the general discussion topics of the time: the fate of slavery, reconstruction, etc.

In 1863 he spends months in New York and New Port with little company besides his caretakers and surgeons (including Edwin Booth, who becomes a dear friend of Badeau) and he writes to Wilson regularly. In this period of perpetual physical pain and loneliness, his close relationship to Wilson becomes apparent.

He mostly reports on military affairs, politics, and his convalescence, and these letters show much insight, especially regarding the future of the South. In addition, these letters demonstrate his friendship with Wilson. Badeau engages in a witty and at times flirty banter regarding their correspondence and intimacy. In these letters he divulges how meaningful their friendship is. In 1864, a breach in their friendship arises, which is not fully explained because Wilson's letters are not part of this collection. Eventurally, they do become friends again, and Badeau returns to writing about the generals he serves, and the war, and the aftermath of the war.

The collection consists of 79 autograph letters from Adam Badeau to Union general James Harrison Wilson, dated 1862 to 1865, most of which were written while Badeau was General Ulysses S. Grant's military secretary in the Civil War. One letter describes the Confederate surrender at Appomattox and the meeting between Generals Lee and Grant. Also included is a letter (1909) by Wilson and a few newspaper clippings about him.