Here's a synopsis of the first 7 years, also from the Yorkville site. Several "fists" here, including first portable PA, first 8x10 cab, first wedge monitor, and a few times they had the world's loudest bas amp (see above linked PDF for details).
Here are some early milestones along that 37-year pathway:
1963
the YSC-1 portable PA column (6x8" speakers, 150 watts, 5.3 Ohms) filled a huge gap. Portable PA was unknown at the time and they could be used with any commercial PA amp.
the "Dynabass", later re-named the YBA-1 "Bass Master" was a tube head (45 Watts rms, no clipping @ 8 Ohms) cleverly designed to please bass and guitar players alike.
1966
the YVM-1 "Voice Master" 4-channel, 45-watt PA head
another "first". But this one had a few extra "firsts". All inputs and speaker outputs were standard 1/4-inch jacks, there were In and Out effects patching jacks, switchable speaker impedance matching and a Master Volume control!
1967
the MX-1, a battery-powered mini-mixer could add 4 channels to any PA
the YBA-3 "Custom Special" (130 Watts no clipping rms @ 4 Ohms) made it the most powerful bass head then on the North American market, and possibly in the world.
the YC-810 (200 watts, 4 Ohms) "Big B" bass cabinet with eight ten-inch drivers was the first of its kind and originally came on a massive tube steel "swivel dolley".
the LS-1 lighting system (8 floods on 2 t-bars with switch controller) was many years ahead of its time.
the TRC-2A "Roto Master", rotating horn box for guitar, was a unique forerunner to the flanger and chorus.
the YGM-1 "Guitar Mate" tube combo (12" speaker, 20 watts no clipping rms @ 8 Ohms) was an instant success and, when replaced by the updated, 25-Watt YGM-3 in 1969, quickly became one of the industry leaders for its quality and versatility.
1968
the YBA-3A, "Super Custom Special" fan-cooled bass head (minimum 250 Watts rms no clipping @ 2 Ohms) could put out over 400 watts if driven hard enough and had to be used with two YC-810 "Big Bs". The 100-pound monster used four 6KG6A TV verticle hold tubes for output and was a "first" for Yorkville, and the world.
1969
the MX-8, a nonpowered 8-channel mono mixer brought club PA into the multi-channel era.
the YPM-1 mono power amp (100 watts @4 Ohms) went with the MX-8 & MX-24.
the MX-24 was the worlds first 24-channel, multi-bus mixer designed specifically for full-scale live sound contracting. Such an operation was run by Pete Traynor from 1969 to 1971 ("Strawberry Fields", "Lighthouse at Varsity Stadium", "Gordon Lightfoot at Massey Hall", "Johnny Winter at Maple Leaf Gardens", "Steve Miller in Toronto", etc., etc., ). With no others known to have been in existance yet, this operation was a "first" in its own right.
the YSR-2 "Signature Reverb" combo (4x10", 2 chan., 45 watts) was a "first" in that it introduced the guitar amp world to one of its most enduring features the Master Volume control.
the "wedge" floor monitor was created for Petes contract system. A later spin-off, the YSM-1 (not to be confused with the present day studio monitor), was another "first", not only because it was a wedge monitor when there were no others, but also because its unique design provided two different up-facing angles.
