I think it goes back, way back, to Thomas Edison in Menlo Park, New Jersey. During one of his experiments with electricity, a big stranger wandered through Edison's outdoor lab, bumped up against a Jacob's Ladder device, and, after a series of unfortunate events that involved massive amounts of electricity, he became a hairy monster with gigantic feet and, as has become apparent, a much longer lifespan.
Like Dr. Frankenstein, Edison alternately loathed and loved his accidental creation. They chatted and ate together on occasion and Edison acted on Bigfoot's behalf when he could not do for himself, such as visits to the haberdasher and the bicycle repair shop.
But Edison could only wring his hands in despair and regret at reports of midnight havoc in local cornfields and watermelon patches, not to mention bicycle tire outlets. (This was a time before the mountain bike and tires just weren't up to the standard we all enjoy today.)
When Edison died, the whole idea behind Menlo Park died with him, at least as far as Bigfoot was concerned. He wanted nothing more to do with New Jersey. But in remembrance of his best pal, he now lives near Menlo Park, California, in a forested area in and around Portola Valley and Woodside.
The locale suits his craving for privacy as well as its proximity to that namesake town. Bigfoot's well-to-do neighbors, the elite of Silicon Valley, are naturally reluctant to invite the scorn of the national media by claiming to have seen him. It's ideal.
His favorite holiday, not surprisingly, is National Gorilla Suit Day, made famous by Mad Magazine cartoonist Don Martin. Sadly the holiday is little celebrated, so he makes do with Halloween.
It is rumors of Bigfoot sightings on Halloween night that brought researchers to Menlo Park.