...What was the first non-1911 pattern semi-auto chambered in .45 ACP?...

Non-1911s they are.

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COLT 1905.

I had one about 1960 or so. It came out of Mexico and had very worn silver grips on it. There was not one spot of blue and the markings on the slide were worn off the left side from being carried Mexican style. The metal was unpitted, just very worn. The rifling in the barrel were just dark lines from being shot. It was all there and worked just fine. I fired one magazine through it and it went bang every time.

It really wasn't a shooter and I was not a collector at the time, so it went by-by in some long forgotten swap. I think I paid $25.00 for it. I bet that old pistol had some stories to tell.

It was a pretty cool design with two toggles holding the barrel to the frame. With the slide off, the barrel was still on the frame held firmly by two wedges.