North Arm Salt Chuck lies at the head of North Arm, an estuary roughly 5 miles (8 km) long at the end of Duncan Canal on Kupreanof Island, about 110 miles (177 km) southeast of Juneau and 13 miles (21 km) west of Petersburg, Alaska. The U.S. Geological Survey recorded the local name in 1960. Duncan Canal extends 22 miles (35 km) northwest from Sumner Strait. The bay was first charted by James Johnstone, the sailing master of HMS Chatham, and named by Captain George Vancouver on August 30, 1793, for his contemporary, British Admiral Adam Duncan.

The Tongass National Forest maintains a public-use cabin on North Arm. The Salt Chuck East Cabin is an A-frame equipped with an oil heater, bunk beds and a rowboat, and sits at the south end of the Portage Mountain Loop Trail. This primitive trail, about 4 miles (6.5 km) long, connects North Arm to the head of Portage Bay. Portage Bay opens onto Frederick Sound on the south side of Kupreanof Island, roughly 25 nautical miles north of Petersburg, and the trail follows a historic overland route linking the bay to Duncan Canal originally cleared by the Civilian Conservation Corps in the early 1930s.

Indian Point, south of North Arm in Duncan Canal, was the site of a Cold War radio-communication station. It formed part of the White Alice Communications System, a U.S. Air Force network of about 80 radio stations built across Alaska. The system used tropospheric scatter for over-the-horizon links and microwave relay for shorter line-of-sight links, with sites marked by large parabolic tropospheric-scatter antennas and smaller point-to-point microwave dishes. White Alice linked remote Air Force sites in Alaska to command-and-control facilities in Colorado, providing two routes to the North American Aerospace Defense Command: Route A ran down Alaska’s southeast coast, through the Duncan Canal station, to a submarine cable linking Ketchikan and Seattle; Route B ran east into Canada. Read more here and here. Explore more of North Arm Salt Chuck and Duncan Canal here: