Panama Canal Zone
The Panama Canal Zone () was an unincorporated territory of the United States from 1903 to 1979, centered on the Panama Canal and surrounded by the Republic of Panama. The zone consisted of the canal and an area generally extending on each side of the centerline, excluding Panama City and Colón, which otherwise would have been partly within the limits of the Zone. Its border spanned three of Panama's provinces. When reservoirs were created to assure a steady supply of water for the locks, those lakes were included within the Zone.
Panama Canal Zone
Through the remainder of the 19th century, the United States landed troops several times to preserve the railway connection. At the same time, it pursued a canal treaty with Colombia (as New Granada was renamed). One treaty, signed in 1868, was rejected by the Colombian Senate, which hoped for better terms from the incoming Grant administration. Under this treaty, the canal would have been in the middle of a 20-mile zone, under American management but Colombian sovereignty, and the canal would revert to Colombia in 99 years. The Grant administration did little to pursue a treaty and, in 1878, the concession to build the canal fell to a French firm. The French efforts eventually failed, but with Panama apparently unavailable, the United States considered possible canal sites in Mexico and Nicaragua.