The panamians were eager to secced from Colombia ( not Columbia ). In exchange for the US support for their independence.
quote from Wikipedia:
The United States under Theodore Roosevelt bought out the French equipment and work to date, and began work in 1904, after helping Panama to declare independence from Colombia in exchange for control of the Canal Zone. A great investment was made in eliminating disease from the area, particularly yellow fever and malaria, and construction of an elevated canal with locks began in earnest. The canal was formally opened on August 15, 1914, with the transit of the cargo ship Ancon.
The canal and the zone surrounding it were originally administered by the United States. However, on 7 September 1977, U.S. President Jimmy Carter signed the Torrijos-Carter Treaty, which set in motion the process of handing over the canal to Panamanian control. Although controversial within the United States, the treaty came into force on 31 December 1999, since when the canal has been run by the Panama Canal Authority (ACP).
source:
http://en.wikipedia.org/wiki/Panama_Canal