A sleek early-1960s Chevy Impala leads a transit bus through the curved concrete throat of the Detroit-Windsor Tunnel in this vivid chrome-era view — the yellow-banded portal sign reading "CANADA — OPEN 19[hrs]" hinting at the round-the-clock international traffic that made this one of the most unique border crossings on earth. Opened in 1930, the Detroit-Windsor Tunnel bored beneath the Detroit River to link the United States and Canada in a single underwater mile — the only international vehicular tunnel in the world at the time of this card's printing, a claim still made in the publisher's own description on the reverse. Detroit's mid-century skyline rises in the background: the turreted guardian tower of the Penobscot Building visible between two curtain-wall office towers, a city still confident in its industrial might just before the upheavals of 1967.