The Lewis Van Tuyl papers contain 101 letters written by Van Tuyl to members of his family during his Civil War service with the 10th Illinois Infantry. The letters span September 1861 to July 1865. Van Tuyl wrote primarily of camp life, skirmishes and battles along the Mississippi River, and his participation in Sherman’s march through Georgia and South Carolina. The collection opens with three letters describing his time at Camp Defiance in Cairo, Illinois. Van Tuyl noted that the area was situated on "low ground" and permeated by "a stench that does not improve the health of the camp" (September 5, 1861). On October 6, 1861, he wrote that the regiment had moved to Camp Morgan in Mound City, Illinois, to escape its own waste (October 6, 1861). Other early letters concern such topics as Union uniforms (September 11, 1861), a visit to a plantation in Kentucky and the activities of slaves living on it (September 23, 1861), and the meals prepared for the company by a cook (November 6, 1861).
After a period spent in the hospital, described in several letters during late-February and early-March 1862, Van Tuyl rejoined the regiment. He gave a lengthy account of action at Tiptonville, Tennessee, during the Battle of Island Number Ten (April 10, 1862), as well as an account of an engagement near Fort Pillow (April 15, 1862). On May 11, 1862, he reported the death of a "valuable man," Major Zenas Aplington, who had been targeted by a sharpshooter during a reconnoitering mission near Corinth, Mississippi. His letter of June 21, , contains a small pencil sketch map of the Union and Confederate fortifications, troop positions, and Union camps during siege of Corinth, Mississippi. Van Tuyl also described the Confederate raid on Holly Springs, Mississippi, and called the Union garrison commander, Colonel Robert Murphy, a "second [Benedict] Arnold" (March 11, 1863). In the summer of 1863, Van Tuyl wrote home concerning frequent marching, pickets, and some aspects of camp life. The collection contains a gap between November 21, 1863, and March 1, 1864, and just six of Van Tuyl's letters cover 1864. In these, he discussed the severe treatment of Union prisoners at the hands of Confederates (March , 1864), the health of the company (April 24, 1864), and money that he sent home to his family (November 9, 1864). On December 16, 1864, he wrote about the regiment's arrival in Savannah, Georgia, and noted that "all approaches to the city are closely guarded and…it can neither be reinforced or evacuated." He also noted that he felt very isolated from news and happenings in the North.
In 1865, Van Tuyl participated in Sherman's March through the Carolinas. In a letter of January 25, 1865, he stated that Sherman was currently in the camp, and "his presence indicates action." He also mentioned the construction of a portable trestle to be used for river crossings. In a later letter, he described the slog through North Carolina's swamps and quicksand and frequent travels over difficult "Corduroy Road[s]." He worried about contracting yellow fever, which he called the "great Hydra Headed monster promised by the Rebels from the beginning" (March 25, 1865). Van Tuyl's correspondence closes with a letter announcing his readiness to return home, dated July 3, 1865, the day before he was mustered out.