Up to and including 1880 the country had a frontier of settlement, but at present the… — Robert P. Porter

Up to and including 1880 the country had a frontier of settlement, but at present the unsettled area has been so broken into by isolated bodies of settlement that there can hardly be said to be a frontier line. In the discussion of its extent, its westward movement, etc., it can not, therefore, any longer have a place in the census reports.

On the closing of the American frontier.