Why did the 1890 census say that the united states no longer had a frontier

The increase in population and the way it has spread across the country have caused the American border to disappear.

Explanation:

The United States Census of 1890 determined that the resident population of the United States was a total of 62,979,766, an increase of 25.5% over the 50,189,209 people listed in the 1880 census.

This increase in population has provoked the provision of free land to citizens and railways by selling cheap land to European farmers. This caused a rapid settlement of the Great Plains. As a result the frontier virtually ended in 1890.

the great wall of china worked as a defense for the feudal states of the zhou dynasty to the north. during the warring states period more walls were put up to defend the borders of the different kingdoms. it was semi successful because despite the wall, the mongols eventually conquered china also the great wall provided protection to the economic development and cultural progress, safeguarded the trading routes such as the silk road, and secured transmission of information and transportation. @jayxboof