Southernmost Point in Continental USA
Key West, Florida
Whenever the winter chill sets records in much of the country, those in the know huddle around the pot-bellied stove-like monument marking the Southernmost Point in the United States.
The marker, actually built to resemble a buoy, stands at furthest south tip of Key West. The monument notes that Cuba is only 90 miles away, and just to its right, a plaque commemorates the brave Cubans who have drowned trying to get to America, "The Leader In Democracy." In the blocks around the Monument are numerous other "Southernmosts" -- hotel, house, restaurant, etc.
On the top of the monument is painted the logo of The Conch Republic. Twenty years ago, Key West, seeking to enhance its reputation as a free-wheeling, fun-loving, party without consequence kind of town, seceded from the United States, declaring itself The Conch Republic. Every April, a ten-day party celebrates the event. But if that's the case, then the Southernmost Point in The US is actually one key up, in Boca Chica.
Update - April 2007: Jacob further clarifies that Key West can only claim to be the southernmost point in the continental US. The big island of Hawaii is farther south.
October 2006: Tipster Robert Burr clarifies for us that the Southernmost Point Marker is NOT at mile marker 0 on US 1. "US1 (Truman Avenue locally), ends one block west of Duval Street (the main drag) at Whitehead Street, at the courthouse. The sign reading "END US1" with a green mile marker zero (often stolen) is located at a four way stop sign which few would consider the end of any road, but in fact, it is the end of US1, at least one mile from the southernmost marker."
And there are slightly further bits of land, though not celebrated with a concrete marker: " Many points at Harry Truman Annex and Fort Zachary Taylor are located further south, but not accessible to traffic. The South Beach Motel, which includes a land fill, actually runs farther south than the marker to be precise." Perhaps these are places that could disappear in the next big hurricane....