His brother-in-law Myles Moylan survived the battle as part of the forces with Major Marcus Reno and Captain Frederick Benteen.

Calhoun was born in Cincinnati, Ohio into a prestigious and wealthy Scottish-American merchant family that included his brother Frederick.

[1] His soon to be brother-in-law George Armstrong Custer had him appointed to first lieutenant in the U.S. 7th Cavalry Regiment, assigned to Company C. Calhoun was known as "The Adonis of the Seventh" due to his handsome features.

He often wrote letters to his brother and to Margaret, or Maggie as she was called, writing with disdain of his limited understanding of complex native culture, adherents to which naturally resisted military conquest.

He often referred to them as "heathens" and desired that one day a post-agricultural population explosion would make hunting-gathering lifestyles unsustainable in the face of Western society.