Proof was originally discovered in 1805 by the Lewis and Clark expedition and presented to President Thomas Jefferson.  Jefferson was an amateur crytozoologist and, impressed by the young primate's intellect, took Proof under his wing, teaching him the sophistication and taste that separates him from his fellow cryptids. 
 
Proof has been alive for more than 200 years and has lived all over the world.  He returns at regular intervals to the Pacific Northwest, where he was originally discovered, hoping to find some hint of his natural family.  He has no memory of his parents.  While searching for them in the late 1960s he was rediscovered by Leander Wight and Werner Daschund.  Together with Wayne Russet and Gloria Wight, the five created the current version of The Lodge with the hope of eventually finding Proof's family. 
 
Proof has known many famous and infamous people.  He travelled for a time with the circus, where he was known as "Gulliver."  It was there that he met and fell in love with fellow sideshow performer, Julia Pastrana.
 
In the first arc of Proof, "Goatsucker", Proof investigates a Chupacabra attack in Minnesota.  This is his first assignment with his new partner Ginger Brown. The Chupacabra, who goes by Nadine, strips people of their skin and impersonates them by wearing it. By the end of the story arc, Nadine kills and impersonates Elvis Chestnut's, the head sheriff of the small Minnesota town, mother. Proof and Ginger figure this out and escort Nadine to The Lodge. While Proof and the Chupacabra talk, it is clear that they knew each other in the past, also referring to Proof as "Gulliver". They offer Elvis a job at The Lodge and he takes it, becoming a partner to Proof and Ginger.