Coba jelasin Nota dari Pembelian Gadsden dalam bahasa melayu dong

Kluger, Richard. Seizing Destiny: How America Grew From Sea to Shining Sea. (2007) ISBN 978-0-375-41341-4

Nevins, Allan. Ordeal of the Union: A House Dividing 1852-1857. (1947) SBN 684-10424-5.

Nichols, Roy Franklin. Franklin Pierce: Young Hickory of the Granite Hills. (1969 2nd. Edition) 8122-7044-4

Potter, David N. The Impending Crisis 1848-1861. (1976) ISBN 0-06-131929-5

Richards, The California Gold Rush and the Coming of the Civil War. (2007) ISBN 0-307-26520-X

Roberson, Jere W. "The South and the Pacific Railroad, 1845-1855." The Western Historical Quarterly, Vol. 5, No. 2, (Apr., 1974), pp. 163-186. JSTOR