Answer:
it is a group. A 'colony' of people. squad, group, gang etc.
Explanation:
It was meant to warn Americans against potential peril in the wake of the 1890 census which coldly stated that there was no longer unexplored wilderness in America (sans Alaska), that there was no longer a contiguous frontier, there was also not an official statement saying that the frontier had been closed because it was merely hearsay.
