I have been wondering this. I know that during WWI 1911’s were built by Springfield Armory and UMC, and during WWII the 1911A1 was built by multiple contractors, but right after WWII Colt was the only company producing commercial Government Models. When did that change? How long did it take for another company to start producing 1911 pattern pistols? Were they any good? Did companies just think there wasn’t a market or did Colt still have some patents that prevented them from copying the design? Kind of like the AR it seemed to take a while but now it appears that everyone and their brother produces them.

Some of the first ones I remember were imports such as Llama and Star.

Llama is a mechanical copy but not fully interchangeable, Star not even close.

Essex frames, commonly used with surplus parts were available in the 1960s.

The first whole guns I recall were the stainless efforts from AMT, Randall, and Vega in the early 1970s.

Patents had run out in time for several Colt design features to be incorporated in the Saive/Browning High Power ca 1929, so it wasn't that.

IIRC, the AMT, which Jim Watson just mentioned, was one of the first to be made in stainless steel. That was in the 70s. One of their models was called the "Hardballer". Some pistoleros like Jeff Cooper, Colonel Charles Askins and Phil Engeldrum wrote about this model but I can't remember what they thought of it as far as performance goes.

Another company called Detonic came along about then too. They made a compact 1911.

Springfield Armory got into the 1911 business a little later on. Early 80s I believe.

The patent on the 1911 design expired on Febuary 17, 1930. Non licensed commercial production started sometime after that.

If you're taking into account foreign licensed copies produced for commercial sales, the Argentinian Fabrica Militar de Armas Portatiles produced their licensed copy of the M1911A1 known as the Sistema Colt Modelo 1927 from 1945-1966, many of which were for Argentinian military/police use but some of which were offered for commercial sale and export.