Portland Head Light has been burning since January 1791, commissioned by George Washington and paid for out of a young federal treasury that could barely afford it. The masons built it from rubblestone hauled off the surrounding headland. It remains the oldest lighthouse in Maine, and the anchor of any portland sunset lighthouse cruise that turns south out of the harbor. Casco Bay was charted as a working waterway long before it was a scenic one. Its islands — reputedly one for every day of the year, in truth closer to two hundred — sheltered fishing fleets, quarries, and a granite trade that shipped south by schooner. Commercial Street was built on filled tidal flats in the 1850s to serve that traffic. The ferry service that still runs from Casco Bay Lines dates to 1845 and is the oldest continuously operating ferry system in the United States. Its mail boat still delivers to island post offices. Portland lighthouse boat tours follow much the same channel the mail has taken for a century and a half. The navigational architecture is the bay's real collection. Spring Point Ledge Light, completed in 1897, is a sparkplug caisson tower standing on a submerged shelf that had wrecked more than a dozen vessels. Bug Light — properly Portland Breakwater Light — wears a cast-iron colonnade modeled on the Choragic Monument of Lysicrates in Athens, an improbable piece of Greek Revival ornament at the mouth of a shipping channel. Ram Island Ledge Light, granite and unpainted, was raised in 1905 after the liner Californian went aground. Halfway Rock sits alone on a ledge four miles offshore, first lit in 1871. The forts read as a second layer. Fort Gorges, a granite hexagon finished in 1865, was obsolete before its guns arrived; rifled artillery had made masonry forts indefensible. It has never been attacked and never garrisoned in wartime. Fort Scammel and the batteries on House Island belong to the same abandoned defensive logic. What makes an evening sailing distinct is the light itself. Casco Bay opens east-southeast, so the sun sets behind the working waterfront and throws the towers into relief against darkening water. Keepers' logs recorded that hour as the moment lamps were lit. A portland sunset lighthouse cruise now traces that same schedule, departing on a timetable written by the horizon rather than the clock, and returning after the beacons have taken over the bay.