Question

What activity ended with the closing of the frontier?

Answer 1

A year after the Oklahoma Land Rush, the director of the U.S. Census Bureau announced that the frontier was closed. The 1890 census had shown that a frontier line, a point beyond which the population density was less than two persons per square mile, no longer existed.

Answer 2

A year after the Oklahoma Land Rush, the director of the U.S census* bureau said that the frontier was closed.

Step-by-step explanation:

*an official count or survey of a population, typically recording various details of individuals.