James Loudon Priest Jr. was born on May 1, 1769, and named for his father, James Loudon Priest Sr. (1737–1821). His father served in the Revolutionary War at Bunker Hill and the Siege of Boston, and preferred to go by the name Loudon Priest (Loudon being his mother's maiden name).

In November 1790, James Loudon Priest, Jr. married Polina Chauncey, and together they had fourteen children, twelve of whom survived infancy. He moved his family from Massachusetts to New York, then to Pennsylvania, before settling in what is now Holmes County, Ohio.

Priest was among the earliest settlers, purchasing 1,000 acres at the Canton Land Office on May 10, 1810. He built his first cabin along the Lake Fork, a tributary of the Mohican River, and soon brought his family to join him—likely including his father. The first cabin proved unsuitable, so another was built a mile west. Once that home was outgrown, he constructed a final cabin just 50 feet from the original, which stood until 1901. At the outbreak of the War of 1812, he built a fort on his property to protect his family and nearby settlers.

In 1814, Priest helped establish the village of Loudonville, reserving twelve central lots for a public park and setting aside land for a cemetery. Records often complicate the father and son's names, but it is most likely the son founded the village and named it after his father.

Priest was also an active Freemason. On November 11, 1818, he received his Master Mason degree at the Wooster Lodge, later advancing to Royal Arch Mason, a title he held until his death in 1822. He died of unknown causes at the age of 53. His estate passed to his wife, Polina, and eldest son, William. He left no will.