Wow, Wikipedia, you got that wrong.
This claim appeared on Wikipedia's front page on May 1, 2015. But if you read the Wikipedia article on the Timeline of the Spanish-American War, you swiftly discover that the first action in the war occurred on April 27.
That day, the USS New York, USS Cincinnati, USS Puritan, and other American naval ships bombard the Cuban city of Matanzas in the Battle of Matanzas. Cuban coastal defenses return fire.