Answer: Woodrow Wilson
The Panama Canal opened officially on August 15, 1914. The planned festivities were largely cancelled due to the outbreak of World War I a few weeks earlier, and Wilson did not attend the ceremony.
“The 10-year endeavor cost $375 million and 5,609 lives, and to many it became the new symbol of American imperial power.” Scott Bomboy, “After 100 Years, Panama Canal Still Symbolizes Executive Power”
While the Canal opened during Wilson’s first term, its creation was largely the result of Theodore Roosevelt’s efforts, as he described it to a group in 1911.
“The Panama Canal would not have been started if I had not taken hold of it, because if I had followed the traditional or conservative method I should have submitted an admirable state paper occupying a couple of hundred pages detailing all of the facts to Congress and asking Congress’ consideration of it,” he said. “In that case there would have been a number of excellent speeches made on the subject in Congress; the debate would be proceeding at this moment with great spirit and the beginning of work on the canal would be 50 years in the future. Fortunately the crisis came at a period when I could act unhampered. Accordingly, I took the Isthmus, started the canal and then left Congress not to debate the canal, but to debate me.” –Theodore Roosevelt in 1911 (Source: “After 100 Years, Panama Canal Still Symbolizes Executive Power” National Constitution Center (August 15, 2014)
Here is an animation demonstrating how the locks in the canal work from PBS “American Experience: TR: The Story of Theodore Roosevelt”
The Panama Canal History Museum has a large collection of photographs and documents about the canal.