This publication releases swath bathymetry and backscatter datasets derived from multibeam bathymetric data acquired by the U.S. Geological Survey (USGS) on the R/V Marcus G. Langseth legs MGL1108 (transit) and MGL1109 in the Gulf of Alaska, and MGL1111 in the Bering Sea. These data were acquired with a Kongsberg Simrad EM-122 multibeam echosounder and Seafloor Information System (SIS) acquisition software. The MGL1108 data were combined with the MGL1109 data during processing and are presented as MGL1109. This data set includes 100-m bathymetry grids generated from processed bathymetry soundings, 100-m backscatter grids generated from coregistered processed backscatter values, extracted center beam bathymetry soundings, and associated metadata. The Gulf of Alaska lines extend from 48.27° N to 57.71° N, 137.81° W to 152.38° W in the northeastern Pacific, including portions of the distal Surveyor and Baranof fan systems, Kodiak-Bowie seamounts, and Aleutian trench near Kodiak Island, AK. The Bering Sea lines extend from 54.04° N to 58.88° N, 166.56° W to 174.04° E, including portions of the Umnak Plateau northwest of Dutch Harbor, AK, central Aleutian Basin, distal eastern flank of Shirshov Ridge, and north face of Bowers Ridge. These surveys were designed primarily for acquisition of multichannel seismic-reflection imaging and ocean-bottom seismometer OBS velocity analysis in support of Extended Continental Shelf (ECS) maritime zone definition. The USGS activities in mapping the ECS are coordinated through the interagency ECS Task Force, comprising representatives from the U.S. Department of State, the USGS, the National Oceanographic and Atmospheric Administration (NOAA), and several other governmental agencies. Further information on the U.S. Extended Continental Shelf (ECS) Project and its activities is posted at https://www.state.gov/e/oes/ocns/opa/ecs/index.htm.