Per capita is the only valid way to compare crime rates in populations of different sizes. Absolute numbers tell you nothing; rates tell you more, more accurately.
Per capita information provides more granular data than just aggregate information. It is often used as an apples to apples comparison between countries with different population sizes.
Do you actually live in America, these statistics are available every year, for almost anyone to easily research, like when they move, start a family, or even get a job.
There are bad neighborhoods in almost any American city, but when you look at crime and an entire city Chicago is quite mild compared to other American cities. The most dangerous cities in America usually stary that way, like New Orleans, St. Louis Missouri, and Baltimore.