By a treaty of 1846 the United States gained transportation rights across the Panamanian isthmus in return for its recognition of Colombian sovereignty in Panama. During the 1840s the isthmus was used as a land bridge by Americans migrating to Oregon and California from the east coast of the U.S. In 1848 an American company was granted rights to build a railroad across the isthmus; construction, begun in 1850, was completed in 1855. Panama won from Colombia a large measure of self-rule in 1855, and in 1863 a new Colombian constitution gave each of its provinces, including Panama, virtual independence. In 1866, however, direct control by Colombia was restored; subsequently, numerous unsuccessful revolts against Colombia took place, partly because of repressive and corrupt rule by Colombian officials and partly because many Panamanians were dissatisfied with the progress of negotiations for digging a canal across the isthmus.
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