The Presbyterian Church, working in its favorite methods, devised campaigns of home missionary enterprise in its presbyteries and synods, detailing pastors from their parishes for temporary mission service in following the movement of the Scotch-Irish migration into the hill-country in which it seemed to find its congenial habitat, and from which its powerful influences were to flow in all directions.

The Congregationalists of New England in like manner followed with Christian teaching and pastoral care their sons moving westward to occupy the rich lands of western New York and of Ohio.

The General Association of the pastors of Connecticut, solicitous that the work of missions to the frontier should be carried forward without loss of power through division of forces, entered, in 1801, into the compact with the General Assembly of the Presbyterians known as the "Plan of Union," by which Christians of both polities might cooeperate in the founding of churches and in maintaining the work of the gospel.
In the year 1803 the most important political event since the adoption of the Constitution, the purchase of Louisiana by President Jefferson, opened to the American church a new and immense field for missionary activity.

This vast territory, stretching from the Mississippi westward to the summits of the Rocky Mountains and nearly doubling the domain of the United States, was the last remainder of the great projected French Catholic empire that had fallen in 1763.

Passed back and forth with the vicissitudes of European politics between French and Spanish masters, it had made small progress in either civilization or Christianity.