Wikipedia:
>4340 steel is an ultra-high strength steel
https://en.wikipedia.org/wiki/4340_steel
The alloy composition calls for 0.2-0.3% molybdenum and expects accuracy to within a few per mille for ten elements. Moly is considered so important that there are entire towns in the United States established to mine it to secure the military supply chain.
Is this true? From the Wikipedia article, the two mines that produce molybdenum as the main product are the two in CO, Henderson and Climax. They have no towns associated with them. Climax is near Leadville, but Leadville existed as a mining town before molybdenum was being mined at any scale. The other mine isn't close to any town that has more than a trailer park of people.
The others mine molybdenum as a byproduct of copper. I guess you could say the Bagdad mine has a company town, but it wasn't made to secure the military supply chain 140 year ago.