what attracts so many hispanics to the chicago area?

[patrick1]

The answer to the question is hiding inside the question: Chicago is what attracted/attracts so many hispanics to the Chicago area. It's a big city forchristssake.

There are not nearly as many Mexicans in New York City or Philadelphia. Chicago really stands out in terms of specifically Mexican population outside the southwest.

The dominant Hispanic groups in NYC are Dominican and Puerto Rican, but we're large enough to have a decent-sized Mexican population too.

Not only Mexicans but a very rapidly expanding population of Central Americans.  Long Island in particular has seen a rapid increase in El Salvadorians.  You take a town like Hempstead that was virtually all black 20 years ago and now is roughly evenly split with Hispanics likely overtaking.   Even within the city limits, Mexicans and other Central Americans (not even counting very large S. American communities) will soon outpace Puerto Ricans and Dominicans.