America's Entry into the War

After maintaining two and a half years of neutrality, events forced the leadership in the US to enter the war on the side of the allies. With large Irish- and German-American communities in the voting population, it made sense for Woodrow Wilson and others to steer the course of neutrality. But events made this difficult. The sinking of the RMS Lusitania in May of 1915 was one such event. Of the 1195 lives lost, 128 were Americans.
Later, so-called "unrestricted" submarine warfare would cost lives and millions of dollars worth of cargo as it made its way to Britain. Even though he had been elected on the slogan "he kept us out of war," Wilson would go to Congress on 2 April, 1917 and ask for a declaration of war against the Empire of Germany.
The two graphs indicate that the economy of the United States made the nation that much more formidable an enemy. Although the Iron and Steel graph predates the years of the war, it indicates that the US was on a path to industrial dominance.