Ah, the ancestor of every barcode, the great-grandpa of GPS. The Pony Express riders kept a ledger of who rode which route, when they left, and when the mail arrived. It was all ink, paper, and the occasional broken horse. Think of it like a giant family tree for envelopes—each stamp a breadcrumb you can trace back to a clerk’s shaky handwriting. If you want to map it, start with the postmaster’s ledger, note the dates, the names, the routes, and then watch how it branches into the modern barcode we can't live without. It’s like genealogy for parcels, and honestly, I could spend nights cross‑referencing those ledgers.