It is necessary to go back to 1958 (A.D.) and the summer of 1959. The concept of using recorded data obtained from a single moving element to provide a ``memorized array'' instead of the multiple-element physical array, was offered to ONR (Aubrey Pryce), whose reaction will be described. The years 1960--68 saw slow (mini-funded) progress at Hudson Labs of Columbia University. Two algorithms were conceived and (mini-)tested; a 6-m towed ``fish'' was built, then progress slowed further at the Hawaii Inst. of Geophysics. Graduate students wrote theses and bootlegged computer time; names will be named and credit will be given. The unquenched urge to ``see'' acoustically the seabed in two or three dimensions is at least almost here, as the next few papers show. Some formerly classified reports may have been released by the time of this meeting.