He also twice served multiple terms in the Virginia House of Delegates, the second series representing Richmond during the American Civil War.

He was born in 1803 near Manchester, in Chesterfield County, Virginia across the James River from Richmond, to William Robertson (1750-1829) and his wife Elizabeth Bolling, who was descended from Pocahontas and John Rolfe.

[11] In 1841, Robertson moved to his wife's home, "Mary's Meadows", just south of Abingdon, in southwest Virginia, and farmed.

[5][12] He was made a Justice of the Peace for Washington County on July 25, 1842,[13] and a trustee of Abingdon Academy in 1843, shortly before his father-in-law's death.

[21] As Virginia struggled with the idea of seceding from the United States, Robertson was a staunch Unionist and tried to prevent its secession.

[4][22] He later characterized himself as a "friend to peace and the Union" and noted that he had actively opposed South Carolina's call for a Southern Convention in 1859.

[4][24] When President Abraham Lincoln made his call for troops on April 15, 1861, Robertson believed the Anti-Coercion scenario met and was "from that time forth zealously active in all measures for the defence of his State.

[25] When Richmond citizens presented a resolution asking their representatives to support a similar bill or resign, Robertson refused.

During Congressional Reconstruction, Robertson was a member of the Committee of Nine, led by Alexander H. H. Stuart, that sought Virginia's readmission to the Union.

It was defeated, but the remainder of the new state constitution (without the former version's pro-slavery provisions) was adopted so that Virginia could rejoin the Union.

[30] Among several Virginians replying, Robertson published Pocahontas alias Matoaka and Her Descendants through Her Marriage with John Rolfe.

The Library of Virginia has his papers as governor and other correspondence, including of the Buena Vista Plaster Company run by his sons after his death.

The special collections of the University of Chicago Library also have many boxes of family correspondence, including with Confederate generals during the Civil War and with various historians, as well as concerning the Loyal Company (of which his father-in-law was a shareholder).