The canal, an engineering masterwork that transformed global commerce, opened on August 15, 1914, connecting the Atlantic and Pacific Oceans and saving ships the long, dangerous trip around South America.
Guests marking the anniversary soaked up the sun at the canal's Miraflores locks, singing "Happy Birthday" to the waterway and snapping pictures of a four-meter (13-foot) chocolate-cake replica of the locks as dancers performed traditional Panamanian numbers.
"Today is a regular day of operations because like every day an average of 35 ships will shorten the distance between the Atlantic and the Pacific," he said.
The Greek vessel Galini inaugurated the canal's second century, traveling the 80 kilometers from the Caribbean Sea to the Pacific, 100 years after the US steamship Ancon opened the waterway.
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"There's not just one Ancon steamer for the centenary of the canal. There are many," said Quijano, who was later to host a VIP gala.
The Suez Canal in Egypt has larger capacity, cutting into Panama's share of global shipping traffic, and recently launched construction on a USD 4-billion "new Suez Canal" running parallel to the original.
Closer to home, Nicaragua, which fought Panama more than a centry ago to host the first canal across Central America, has reemerged as a modern-day rival.
The country has launched plans for a USD 40-billion, Chinese-built canal that would be able to handle modern mega-freighters too big for the Panama Canal's current dimensions.
The USD 5.3-billion expansion will allow it to handle so-called "Post-Panamax" ships with a capacity of up to 15,000 containers, instead of the current maximum of 5,000.
But the project has been plagued by delays, strikes and a bitter dispute over USD 1.6 billion in cost overruns with the consortium of companies carrying out the upgrade.