Sumdum is a historical Tlingit village of the S’awdaan Kwáan located north of Powers Creek at the northern end of Endicott Arm where it meets Holkham Bay in Tracy Arm-Fords Terror Wilderness, about 70 miles (113 km) north-northwest of Petersburg and 49 miles (79 km) southeast of Juneau, Alaska. Powers Creek rises at the terminus of Sumdum Glacier and flows southwest for 2 miles (3.2 km) to the eastern shore of Endicott Arm. The Tlingit name for the creek was Si’t-qu. Holkham Bay was named in 1794 by Captain George Vancouver after Holkham, a village in Norfolk, England. The Tlingit knew the bay as Sum Dum, reputedly for the sound of ice calving from glaciers. Endicott Arm was named in 1889 by Lieutenant Commander Henry B. Mansfield of the USCGS Carlile P. Patterson after William C. Endicott, Secretary of War under President Grover Cleveland. Powers Creek was named in 1906 by Arthur C. Spencer and Charles W. Wright of the US Geological Survey after a local prospector. The bedrock forming the eastern shore of Endicott Arm belongs to the western metamorphic belt, which runs parallel to and adjacent to the southwestern side of the Coast Plutonic Complex. At Powers Creek, the rock consists mostly of phyllite and shale metamorphosed from sediments during the Permian to Cretaceous periods, about 300 million to 66 million years ago.

At least 17 geographically distinct Tlingit clans existed in Southeast Alaska prior to Euro-American contact. The Sumdum clan inhabited Holkham Bay and Endicott Arm, using seasonal fish camps in addition to the main village at Powers Creek below Sumdum Glacier. Prospectors discovered gold in Powers Creek in 1869, and the placer deposits were worked intermittently until 1911. In 1880 John Muir visited and described the Sumdum village as occupied by 37 Tlingit of the Wolf moiety who subsisted mostly on salmon and seals. That same year, more gold was discovered across the bay from the village at present-day Sanford Cove, near a traditional family fish camp. In 1893 a large mining facility was developed at Sanford Cove to support the Bald Eagle mine, which employed up to 20 men by 1894. By 1900 the population of the mining settlement—confusingly also called Sumdum—had reached 137, the majority of whom were Sumdum Tlingit. This large Tlingit population suggests that family groups from the dispersed Sumdum settlements in Endicott Arm had become centralized at the mining camp. The mine operated until 1903, after which most of the population left the region. By 1931 no Sumdum remained in the area, and by 1946 no one from the village was still alive.

In 1980 Congress designated 653,179 acres (264,332 ha)as the Tracy Arm-Fords Terror Wilderness. Managed by the Tongass National Forest, the area is accessible only by motorboat, large vessel, commercial cruise ship, or floatplane. Tracy and Endicott are two long, narrow fjords confined by steep rock walls and glacier-covered mountains. About 75% of the wilderness is considered alpine, including 20% glaciers and snowfields. At the head of both fjords, tidewater glaciers calve regularly into the sea, producing floating icebergs that often block access. The area supports breeding colonies of pigeon guillemot, Arctic tern, and pelagic cormorant, as well as mew, glaucous-winged, and herring gulls. Rocky islets and points host nesting black oystercatchers. Humpback whales, seabirds, and common and red-throated loons feed in Holkham Bay. Read more here and here. Explore more of Sumdum and Endicott Arm here: