John Preston, eldest son of William and Susanna (Smith) Preston, was born in 1764 at "Greenfield" in Botetourt County, Virginia. He periodically served in the Virginia militia throughout his lifetime. Preston was elected a member of the Virginia House of Delegates, representing Botetourt County in 1783, as well as Montgomery County in 1791 and again in 1803-1804. He served as a member of the Virginia Senate from 1792-1799.

In 1792, Preston was named as a trustee in the act that established Christiansburg, Virginia in 1792, and served as a clerk of its first Board of Trustees. In 1798 he served as a trustee in the act that established Blacksburg, Virginia. In 1795, Preston became a Lieutenant Colonel, commanding the Third Regiment of Artillery. In 1799, he was elected Brigadier General, and given command of the brigade for Wythe, Montgomery, and Monroe Counties.

Later in 1810, Preston was appointed by the Virginia General Assembly to be the Treasurer of Virginia, serving until 1819. An audit of the treasurer's books found that Preston's accounts were in arrears, and a judgement was issued against Preston for 87 thousand dollars. To meet the obligation, Preston transferred a number of properties to trustees, who were to oversee their sale and the payment of funds into the treasury.

Preston married Mary Radford in 1798, and after her death in 1810, married Eliza Ann Carrington Mayo in 1811. He had seven children with his first wife and one with his second. When not on active military duty, Preston resided at "Smithfield" with his mother until his marriage, after which he lived at "Horseshoe." He died at Greenfield in 1827.