Lester Sebastian Willson was born in Canton, New York on June 15, 1839. His parents, Ambrose and Julia Willson had at least two other sons, Davis and George. Lester enlisted as a private in the Company A, 60th New York Volunteer Infantry during the Civil War and spent the early months guarding the Baltimore and Ohio Railroad in Maryland. He rose quickly in rank, receiving a warrant as second sergeant September 9, 1861; lieutenant October 3, 1862; first lieutenant and adjutant November 17, 1862; captain August 2, 1864; lieutenant-colonel October 1, 1864; colonel May 17, 1865. He saw combat at Antietam and Chancellorsville, where he was wounded in May 1863, but returned to his regiment after Gettysburg where he remained for the rest of the war. At the war's end Willson was brevetted a brigadier general and administered the Soldier's Home in Albany, New York . In 1867 he moved to Montana Territory to join his brother Davis in the mercantile business at Bozeman. Willson entered into a partnership with Loren W. Tuller and Charles Rich at Bozeman, eventually replacing both men to become a sole proprietor. He also served in the state legislature and with the state militia. He married in 1869 Emma D. Weeks and the couple had three children; George (who died as an infant), Lester Eugene, and Fred Fielding. Lester S. Wilson continued to operate his business until his death on January 26, 1919.

The first volume of Willson's diaries contains entries made from July 3, 1863 to September 5, 1864, with substantial gaps. Willson's terse entries describe his final days at Canton, New York, recuperating from a wound he received at Chancellorsville up to his reunion with the 60th new York Infantry in northern Virginia on July 11, 1863. The diary resumes on June 26, 1864 as Willson's regiment prepared to move on Confederate positions guarding the approaches to Atlanta through their subsequent capture of the city. These entries cover in some detail the construction of field works and battle actions at Peach Tree Creek. The second diary begins on November 3, 1864 and ends on May 2, 1865, again with substantial gaps. Willson records his experiences on General William T. Sherman's march from Atlanta to Savannah on the Georgia coast. The actual surrender of Savannah was not recorded by Willson, but the subsequent march from that city to Columbia, South Carolina received many entries. The diary concludes with the 6oth New York on their campaign into North Carolina and the surrender of the Confederate army of General Joseph E. Johnston. Willson describes the logistics of marching with Sherman's army, the destruction of property by Union troops, the liberated slaves who accompanied the army. As a staff officer, Willson also touches on the arguments and in-fighting among officers on matters of promotion and command organization. A folder of laid-in material from the second diary consists of numerous receipts for the shipment of bodies home from the front, regimental record notes, and an original hand signed battle report by Col. Abel Goddard, 60th New York Infantry, for his regiment's part in the battle of Resaca, Georgia on May 15, 1864. Officers mentioned most frequently in Willson's diaries include Goddard, Col. David Ireland, 137th New York Infantry, and Capt. Loren Tuller, 60th New York Infantry.