Andrew Beahrs makes the case:
Twain didn’t just want mussels; he wanted steamed mussels, from San Francisco. He wanted terrapin from Philadelphia, stewed with sherry and cream (the recipe’s main rival, from Baltimore, omitted the cream—Twain loved cream). He wanted partridge from Missouri, shad from the Connecticut River, and perch and canvasback ducks from Baltimore. The list went on. These were things that depended on the grasslands, woods, and waters of especially American places. And they were things that, in Twain’s youth, could be found nowhere else.
Beahrs is author of Twain’s Feast: Searching for America’s Lost Foods in the Footsteps of Samuel Clemens, which I have just purchased on Amazon.