The seabed mapping side scan sonar, conceived and developed in the 1950s at the U.S. Navy Mine Defense Laboratory (USNMDL) [Commander and Sternlicht, J. Acoust. Soc. Am. 137, 2307 (2015)], was inspired by the Royal Navy ASDIC Type-162, a late-WWII hull mounted side-looking sonar capable of recording the silhouettes of bottomed U-boats. The commissioned U.S. Navy C-MK-1 SHADOWGRAPH, which operated in the Megahertz band and employed curved apertures for cross-track focusing, represents the first in a long history of military and commercial innovations. Commercial side scan sonars, typically operating in the tens or hundreds of Kilohertz, reached the marketplace in the 1960s. The SHADOWGRAPH series led to the Navy’s AN/AQS-14 and French DUBM-series mine detection sonars, and the active tow vehicles of the C-MK-1 served as test platforms for the first synthetic aperture sonars (SAS) fielded at USNMDL (now the Naval Surface Warfare Center Panama City Division) during the 1970s. Through the present day these systems, military and commercial, have been augmented by revolutionary: developments in swath bathymetry side scan sonar, multi-beam echo sounders, and SAS; signal processing advances in acoustic tomography and spectroscopy; and information processing advances in environmental characterization, automatic target recognition and seabed change detection.