Locusts have been extinct in North America since about 1930.
The biggest plague used to be the Rocky Mountain locust, which would cover every surface for days, utterly destroying farms. Those went extinct in about 1905. The High Plains Locusts went extinct in about 1930. [1]
There are various theories about why they went extinct -- something to do with what the settlers and farmers were doing to the land. But it wasn't an obvious culprit like pesticide, which wasn't really in widespread use until about the 40s.
The biggest plague used to be the Rocky Mountain locust, which would cover every surface for days, utterly destroying farms. Those went extinct in about 1905. The High Plains Locusts went extinct in about 1930. [1]
There are various theories about why they went extinct -- something to do with what the settlers and farmers were doing to the land. But it wasn't an obvious culprit like pesticide, which wasn't really in widespread use until about the 40s.
1. https://en.wikipedia.org/wiki/Rocky_Mountain_locust