Jack Bay is a deglaciated inlet surrounded by the Chugach Mountains that extends about six miles (10 km) southeast from Valdez Arm, about 70 miles (113 km) east-northeast of Whittier and roughly 15 miles (24 km) by water from Valdez, Alaska. Valdez Arm is a passage connecting Prince William Sound and Port Valdez. Intertidal mudflats fill the head of Jack Bay and boulders are scattered across the shallows. Geologically, the bay is aligned with a contact fault in the Southern Margin Composite terrane, which has traditionally been mapped as the boundary between the Chugach and Prince William terranes. However, recent dating of detrital zircons suggests the fault in Jack Bay may not mark the terrane boundary. The southern shore of the bay consists of Late Cretaceous sedimentary rocks of the Valdez Group, mostly turbiditic greywacke sandstone and slate. These rocks are cut by quartz veins that carry gold, pyrite, pyrrhotite and arsenopyrite. The northern shore consists of Paleocene to Eocene basaltic turbidites of the Orca Group. Part of the bay is now an Alaska State Marine Park.

The Chugach people, an Alutiiq (Sugpiaq) group, have lived around Prince William Sound for millennia, and the Valdez area was part of their homeland. In 1790, Salvador Fidalgo named Valdez Arm after the Spanish naval officer Antonio Valdés y Fernández Bazán. In 1898, Captain William R. Abercrombie of the U.S. Army named Jack Bay, reputedly for W.G. Jack, a prospector then searching for gold. That year, steamship companies promoted the Valdez Glacier Trail as the best route to the Klondike and Copper River gold fields, and the town of Valdez grew to serve the rush. In 1983, state senator Vic Fischer sponsored legislation that created the first Alaska marine parks, 13 in all, to protect natural, cultural and scenic values while promoting recreation and tourism. Jack Bay’s park was established in 1990. Several parks lie in Prince William Sound and Resurrection Bay. Dozens of state marine parks now dot the coast, from Joe Mace Island State Marine Park east of Wrangell to St. James Bay State Marine Park, about 35 miles (56 km) northwest of Juneau on the west shore of Lynn Canal. Most are undeveloped, and they range from exposed coastline to sheltered embayments like Jack Bay.

Jack Bay State Marine Park covers 1,544 acres (625 ha) under its legislative designation, including 811 acres (328 ha) of uplands and 733 acres (297 ha) of tidelands. Nearby lands lie within the Chugach National Forest, which Theodore Roosevelt created in 1907 and which now covers about 5.4 million acres around Prince William Sound. The Alaska Statehood Act allowed the state to select national forest land for recreation and community use, and the state set aside part of that allowance for marine parks. The uplands are managed for public recreation and fish and wildlife habitat. The park offers campsites, toilets, fishing, kayaking and wildlife viewing. It has no road access, so visitors arrive by boat or floatplane. An island in the middle of the bay has four campsites in a protected bight on its southern end. A rustic public-use cabin that sleeps six is operated by the Forest Service at the east end of the bay. The tidelands are managed to protect wildlife habitat and provide access to public recreation areas. The bay is an important source for commercial and recreational fisheries, and much of its shoreline provides herring spawning and salmon rearing habitat. The bay also has seven anadromous streams, a bird rookery and seal habitat. Read more here and here. Explore more of Jack Bay and Valdez Arm here: