Interchangeable parts were first used in what industry?
guns (muskets)
steamboats
horseshoes
wagons

Interchangeable parts were first used in the guns (muskets) industry.

Explanation:

The initial assembling of guns was itself in the first place done using distinct parts that simply worked in synchronous during the functioning of the gun. Having interchangeable parts allowed the owners of the gums and militias to replace them for repair without having to replace the entire weapon. This advancement led to guns becoming available at the cheapest prices and thus, everyone kept guns for their safety.

It was a combination of conquests and alliances