John Porter McCown was born near the town of Sevierville, located in Sevier County, Tennessee.

In September 1835 he entered the United States Military Academy at West Point, and graduated in July 1840 standing tenth out of 42 cadets.

[2] McCown fought during the Mexican–American War and participated in the Battle of Cerro Gordo near Xalapa, Veracruz.

[1] After the war McCown served along the Rio Grande on frontier duty,[2] and he was promoted to captain on January 9, 1851.

He was appointed a captain in the artillery of the Confederate Army on March 16, and then promoted to lieutenant colonel on May 9.

He was promoted to brigadier general on October 12,[1] and he marched his brigade to Columbus, Kentucky, and on to the Battle of Belmont on November 7.

Amid the criticism, McCown was accused of drunkenness and was replaced by William W. Mackall during the Battle of Island Number Ten.

Foote called his son's letter a "patriotic act" in "these days of general fault finding and vulgar crimination".

[1] A bird, McCown's longspur (Rhynchophanes mccownii), was named in his honor in 1851, after he collected the type specimen.

In 2020, it was renamed "thick-billed longspur" by the American Ornithological Society, due to his Confederate associations.