The Southern Alaska Lithosphere and Mantle Observation Network (SALMON) is a deployment of 28 broadband, direct‐burial posthole seismometers in the Cook Inlet region of the southern Alaska subduction zone. Here we describe the objectives of the project, the deployment strategy, and station design. We analyze time‐dependent and frequency‐dependent seismic noise for the first year of data at 18 SALMON stations, 11 of which are inside Cook Inlet basin and 7 of which are outside the basin. We compare noise at the SALMON stations with four previous collocated seismic stations, two Transportable Array stations, and one Global Seismographic Network station. The type of site, notably surface bedrock versus sedimentary basin, has the strongest impact on seismic noise levels across all periods and especially on horizontal components at long periods (). Seismic noise and earthquakes recorded by SALMON stations reveal amplification of seismic waves in Cook Inlet basin. Aftershocks of an 7.1 intraslab earthquake augment a catalog of local earthquakes to be used for source inversions and seismic imaging of the complex seismic structure in the Cook Inlet region.