Avery County has the distinction of being the 100th and last county to be formed in the state of North Carolina. It was named for Colonel Waightstill Avery of Burke County, North Carolina. 

The first attempt to form Avery County came in 1856. Legislation was introduced into the General Assembly that year. Forming counties in the western part of North Carolina was a long and arduous process. Representatives from the eastern part of North Carolina were opposed to new western counties. Not only did new western counties erode the east's power base, but funds for internal improvements as well. In January 1857, the proposal was defeated. A couple of years later, a new bill was introduced for a new county by the name of Mitchell. This act was passed in 1861. Banner Elk and everything north was a part of Watauga County, while everything else was a part of Mitchell County.

The original county seat for Mitchell was located at Childsville (with a name change to Calhoun). The area that encompasses Childsville today is under the Avery County Airport.

It was not until the first decade of the 20th century that talk began once again of plans to split the area into a new county. As early as 1909 there was legislation for a new Hoke County or Park County. Eventually, the name of Avery County was agreed upon, and the new county was created by the General Assembly on February 23, 1911.

Parent counties and their formation dates include: Clarendon in 1729; New Hanover in 1729; Bladen in 1734; Anson in 1749; Rowan in 1753; Surry in 1770; Burke in 1777; Wilkes in 1777; Ashe in 1799; Yancey in 1833; Caldwell in 1841; Watauga in 1849; and, of Mitchell in 1861. Early historian John Preston Arthur believed that when Avery was created in 1911, it had been subdivided ten times, “which is a record probably unsurpassed."

As of 2013, Avery County had a population of 17,713 people and encompassed 247 square miles. The highest point in the county is Grassy Ridge Bald, at 6,165 feet above sea level. Beech Mountain is the highest incorporated community east of the Mississippi River, and at 3,606 feet, Newland is the highest county seat in the eastern United States.