The Spanish-American War of 1898 ended Spain's colonial empire in the Western Hemisphere and secured the position of the United States as a Pacific power.
During World War I, 116,516 US soldiers were killed and 204,002 were wounded. If you add those two numbers together, the total number of US soldiers killed or wounded was 320,518.
You can represent that as a fraction of the current population of Chicago like this:

For simplicity's sake (since I assume the Chicago population number is an estimate), let's round the number of soldiers killed or wounded down to 300,000. That would look like this:

We can simplify that down a lot by dividing the number of soldiers and the number of Chicagoans by the least common denominator of 300,000. That would give us this fraction:

So for every 1 US soldier killed or wounded in World War I, there are 10 Chicagoans living in the city today.
<span>According to Latané and Darley (1968), you will first experience the bystander effect to offer assistance in an emergency. This effect will only happen if the presence of that person is not needed making them feel discouraged to hep further especially if he or she could not help in an emergency situation. The main cause is that there is a clear division of responsibility and social influence.</span>
During the time of the war, the Allied and Axis Powers were the primary belligerents, but the United States still had their "hands-off" stance with international affairs. Though the United States did not directly fight in the war until 1918, they did assist their allies in Great Britain by secretly sending supplies by sea vessels across the Atlantic.
In 1915, a German U-Boat sank the RMS Lusitania, a British ocean liner, carrying British and American citizens to Liverpool. This was ultimately the determining factor for America to join the war, as it put America and Germany on thin ice. America ordered Germany to stop their U-Boat campaign, and when the commenced it again, America entered the war to stop them once and for all.