As in, where is he?
His namesake may still ply the RoA, but his creation's Island has long gone the way of Sparrows.
He's known for a few locations in his life - grew up in Missouri, piloted a boat before the outbreak of the Civil War even. Eventually traveled the world and settled down in the East.
But before that he was a Californian. You could almost call him THE Californian from the period. He came over with the silver rush in Nevada, drifted into the Sierras for the gold rush, experienced life in the hills in nearly every kind of way possible and eventually even launched his lecturing career in San Francisco that would eventually lead to his writing career. A few of his books - Roughing It specifically - and MANY of his short stories are the backbone of California history.
Where is he?