Well, being the only country left with any manufacturing after a catastrophic world war is one major reason.
Also, navigable waterways. Transporting goods by water costs 1/100th what it costs to transport over land. After the US established a corp of engineers to dredge our waterways to make them passable, the ability to transport goods increased substantially, making internal trade extremely cheap.
Also, navigable waterways. Transporting goods by water costs 1/100th what it costs to transport over land. After the US established a corp of engineers to dredge our waterways to make them passable, the ability to transport goods increased substantially, making internal trade extremely cheap.