In 1813 he left his law studies behind and entered the Army as a Captain of the 35th Infantry during the War of 1812. Isaac was honorably discharged in 1815 after which he continued his law studies. He then moved first to Virginia and then to Louisiana.
In New Orleans, Louisiana he married Catherine Lawn Layton the daughter of Robert Layton and Susan Gilchrist on November 20, 1828. They had six children.
In New Orleans Isaac became one of the leading attorneys of the time. He went on to be the Attorney General of Louisiana from 1824 to 1829 and then again in 1843 to 1846. In 1844-1845 he was a member of the Constitutional Convention of Louisiana. He served the Louisiana House of Representatives from 1845-1846 and became a Supreme Court Judge in 1850.
Isaac was one of the key promoters for the construction of the railroad from New Orleans to Jackson, Ms. He was a well respected and prominent land owner. He contributed to many charities among which was the donation of the land for the Methodist Episcopal Church in Carrollton, La.
Isaac remarried in 1845 after the death of Catherine in 1842 to Margaret Hewes. Who was the step mother of his deceased wife, Catherine Lawn Layton.
Isaac died in 1852 aboard the steamboat the St. James, which was involved in a race. The steamboat exploded and burned on Lake Ponchartrain.
The children of Isaac Preston and Catherine Lawn Layton were:
Isaac Trimble Preston who died as an infant
Robert Layton Preston
Thomas Layton Preston
Buxton John Preston
Isaac T. Preston
The Prestons of Smithfield and Greenfield in Virginia by: John Frederick Dorman
The Litchfield Historical Society
The Louisiana Advertiser- Historical Newspaper