The Octavius Leland diaries contain two volumes of near daily entries, spanning October 6, 1863, to June 20, 1865. The two volumes contain a total of 232 written pages. The first volume covers October 6, 1863-September 12, 1864, and the second volume spans September 13, 1864-June 20, 1865. Volume one, which includes 23 newspaper clippings in its front pocket, begins with Leland's travel by train from Elgin, Minnesota, to the barracks at St. Louis, Missouri, during which time, his bag, flute, clothing, and personal effects were stolen. Entries for October 1863-May 1864 describe Leland's time in St. Louis, including his concerts with the regimental band, visits to the city, and military duties. On November 10, 1863, he gave an account of his first visit to downtown St. Louis; he noted with awe the newly built Lindell Hotel with "cars that run to every room," and enjoyed the view of the city from the dome on top of the courthouse. On January 18, 1864, he described a visit to a St. Louis "museum," where he saw a bearded woman and the "Albino Twins of black parents."
Despite the theft of his flute, Leland mentioned playing in several band performances, including the funeral march of "Maj. Brown" (November 7, 1863) and a commemoration of the Battle of Pea Ridge (March 8, 1864). During the latter performance, he was pleased by a "general waiving [sic] of handkerchiefs from the ladies" as he played through the streets. However, on June 1, 1864, a doctor advised him to "quit blowing the fife for awhile" in order to halt dizziness and fainting spells.
During his time in St. Louis, Leland's military responsibilities were light, and allowed him time to sell fruit and carved rings to make extra money (March 9, 1864). By May 1864, however, Leland's regiment was sent to a series of camps in Tennessee, Mississippi, Louisiana, and Alabama, taking part in some minor engagements with guerillas and with Forrest's cavalry, in the Battle of Nashville, the defense of Memphis during Forrest's raid, and the Siege of Mobile and capture of Fort Blakely. The most notable aspect of Leland's service, however, was his long and ultimately unsuccessful bout with disease. He suffered particularly after July 1864; the second volume of Leland's diary chronicles near constant sickness, including diarrhea and respiratory problems. Too weak for duty much of the time, Leland was assigned to assist ambulance personnel, and to other support roles for the regiment. Despite the length and evident severity of his sickness, his requests for a discharge were repeatedly denied, and his Captain apparently believed that he was attempting to shirk his duty. He died of the effects of chronic diarrhea on August 12th, 1865, three days before he was to be mustered out.