Here is a historical photo which leads into even more:

On 11 July 1934 President Franklin Delano Roosevelt was aboard the U.S. cruiser Houston as it transited the Panama Canal en route from Annapolis, Maryland, to Portland, Oregon.  This was the first passage through the canal by a president of the United States while in office.  Military honors were rendered at Miraflores as the warship paused before locking down to the Pacific.  The Houston had embarked Roosevelt and his party at Annapolis on July 1st, proceeding to the canal via Cape Haitien, Mayaguez, San Juan, St. Thomas, St. Croix, and Cartagena.  After a day tour at Balboa on the 12th, the president re-embarked the Houston, and the cruiser got under way at 5:30 p.m. for Portland via Cocos Island and Honolulu.  While in office, President Roosevelt was to make four more visits to Panama, two aboard the Houston in 1935 and 1938 and two aboard the cruiser Tuscaloosa in 1940.  The Houston, launched by Newport News Shipbuilding & Dry Dock Co. in 1929, made here final transit of the canal in 1939.  A year later the ship was posted to the Philippines as flagship of the Asiatic Fleet.  Following several combat actions against the Japanese during the first few weeks of World War II, the Houston was lost in the Battle of the Java Sea in late February 1942.  Having battles against fare superior forces, the heavy cruiser became on of the most honored ships of the war, winning two battle stars and a Presidential Unit Citation.

Photo and narration from the book Ships of The Panama Canal, by James L. Shaw

Note the troops lined up off the east Miraflores Locks wall.  No swing bridge built yet and Fort Clayton can be seen in the distance.

And there is more to this story of FDR's visit to the Canal Zone......

From the Panama Canal Review - Summer 1977:

A few years before the 25th anniversary of the Canal, President Roosevelt arrived in Balboa aboard the U.S.S. Houston.  He was presented, by Canal officials, with an album showing Canal scenes of the construction era and matching pictures of the same areas showing the completed job. Fascinated with the contrast, he suggest there existed in these before and after scenes, the makings of a fine stamp series which could be used to commemorate the 25th anniversary of the opening of the Panama Canal.

The Governor of the Canal Zone, on December 7, 1938, approved the separate scenes of "before" and "after" for a series of 16 denominations for the ordinary stamps and six values for airmail stamps.  (See the stamps)

Another piece of our Canal Zone history.