How did the frontier differ from the settled areas along the east coast?

In 1890, described it as “the part of county which fronts or faces another country or unsettled region, extreme part of a country.” In the 19th century it was statistically classified as an area having no fewer than two but no more than six Europeans per square kilometer. The United States Census Bureau defined areas with lower population densities as “unsettled” and on this basis marked the frontier were no longer the exclusive domain of explorers, missionaries, and trappers, but settled homesteads were relatively rare and widely dispersed.