Under the Ordinance of 1787, Illinois’s northern boundary was an east-west line from the southern tip of Lake Michigan at approximately 41° 38' to the Mississippi River. When Illinois applied for admission to the Union, the bill originally included that boundary, but while it was pending in the House, Illinois Territory delegate Nathaniel Pope pushed to move the line about 61 miles north to 42° 30'. He believed Illinois needed a firm footing on Lake Michigan, tying its interests to northern commerce through the Great Lakes and offsetting the influence of southern trade on the Mississippi and Ohio Rivers in the event of future internal conflict. Pope argued that this addition would strengthen the perpetuity of the Union by connecting Illinois with Indiana, Ohio, Pennsylvania, and New York through the lakes. His amendment passed easily, and the Enabling Act was approved on April 18, 1818. Illinois thereby gained 14 counties and 8,500 square miles, including ports and the future cities of Chicago, Rockford, and Freeport. This added northern territory later helped shape Illinois politically in favor of national unity and against slavery during the Civil War period, and it was important in Abraham Lincoln’s nomination in 1860.