Ohioan John Potts Slough was a brigadier-general in the Union Army during the American Civil War.
Born on February 1, 1829, Slough spent his youth in Cincinnati, Ohio, where his father, Martin Slough, had settled by 1806. John Slough received an education in the city's public schools and briefly attended Cincinnati College. Slough eventually graduated from the Cincinnati Law School and became a practicing attorney in Hamilton County, Ohio.
In 1850, Slough embarked upon a career in politics, winning election to the Ohio legislature. Having a bad temper, Slough struck another member of the legislature, resulting in Slough's expulsion from the body. In 1852, he became the secretary of the Central Democratic Committee of Ohio.
In the mid 1850s, Slough moved to the Kansas Territory. His life there is unknown, but he might have participated in Bleeding Kansas. In 1860, he moved to Colorado, settling in Denver City. He opened a law practice, but with the American Civil War's outbreak, he immediately joined the Union Army, serving as a captain of the First Colorado Volunteer Regiment. In August 1861, officials promoted him to the rank of colonel of the regiment. In early 1862, Confederate forces launched an invasion of the New Mexico Territory. To support Union soldiers already in New Mexico, Slough marched his regiment to Fort Union in New Mexico, where he assumed command of the fortification. The commander of the Department of New Mexico, Colonel Edward R.S. Canby, ordered Slough to remain at Fort Union. Learning that a Confederate force under the command of William Read Scurry was advancing on the fort, Slough left the fort and attacked Scurry's men at Glorieta Pass. Slough was victorious in the battle. Hearing of Slough's movement, Canby ordered Slough to return to Fort Union. Slough immediately resigned his commission out of fear that he would be prosecuted for violating Canby's earlier order.
Slough then proceeded to Washington, DC, where officials placed him in command of a brigade. He participated in the Valley Campaign of early 1862, seeing no real combat as his force was stationed at Harper's Ferry, Virginia (modern-day West Virginia) and did not come under attack. Officials promoted Slough as a brevet brigadier-general and then a full brigadier general in 1862. In the autumn of 1862, Slough became responsible for the military government over Alexandria, Virginia. He remained in this position until the war's conclusion.
In 1865, President Andrew Johnson appointed Slough as the chief justice of the Supreme Court of the New Mexico Territory. Slough quickly developed several political enemies, most notably William Logan Rynerson. After one dispute between these two men, on December 17, 1867, Rynerson murdered Slough.