Vest was best known during his lifetime for his a "man's best friend" closing arguments from the trial in which damages were sought for the killing of a dog named Old Drum on October 18, 1869.

However, while en route, he stopped in Pettis County, Missouri, where he defended a young African-American man accused of murder.

When the Civil War broke out Vest was a strong advocate of maintaining slavery during the Missouri secession crisis, and eventually sided with the Confederacy.

Vest's "Eulogy of the Dog"[1] is one of the most enduring passages of purple prose in American courtroom history (only a partial transcript has survived): Gentlemen of the jury: The best friend a man has in this world may turn against him and become his enemy.

The people who are prone to fall on their knees to do us honor when success is with us may be the first to throw the stone of malice when failure settles its cloud upon our heads.

The one absolutely unselfish friend that a man can have in this selfish world, the one that never deserts him and the one that never proves ungrateful or treacherous is his dog.

If fortune drives the master forth an outcast in the world, friendless and homeless, the faithful dog asks no higher privilege than that of accompanying him to guard against danger, to fight against his enemies, and when the last scene of all comes, and death takes the master in its embrace and his body is laid away in the cold ground, no matter if all other friends pursue their way, there by his graveside will the noble dog be found, his head between his paws, his eyes sad but open in alert watchfulness, faithful and true even to death.Vest won the case (the jury awarded $50 to the dog's owner) and also won its appeal to the Missouri Supreme Court.

He was re-elected for three more terms in 1885, 1891 and 1897 and remained a US Senator until March 4, 1903, when he retired from public life due to ill health.

He introduced and eventually helped pass legislation that required the Secretary of Interior to submit concession and construction contracts to the Senate for oversight thus stifling potential corruption and abuses.

[4] On August 9, 1904, Vest died at his summer home in Sweet Springs, Missouri, the last living Confederate States Senator.