So y'all know out the capitals AU, well this kinda ties in with that. Anyways all cities within a certain state are siblings, example New York city & Albany. 

I only have three states done so far sorry! Also my home city is a little difficult to explain, but you'll get it eventually. 

Ohio 

Cleveland, 1796 (1)

Dayton, April 1st, 1796 (2)

Columbus, 1797 (3)

Cincinnati, December 11, 1788 (4)

Akron, 1825 (5)

Toledo, 1833 (6) [the fact that he's the youngest is so cute I just *inhales*]

Indiana 

Fort Wayne, October 22, 1794 (1)

Evansville, 1812 (2) [what an unfortunate year to become a city lol]

Indianapolis, 1821 (3) [did you know? Indianapolis means indiana city]

Lafayette, 1825 (4)

South Bend, 1831 (5)

West Lafayette, 1836 (6)

[Explaining time - technically both Lafayette & West Lafayettes population is below 100,000 {the number you need to be "alive"}, but even though that are "separate" entities, Lafayette as a whole has over 100,000 pop. So yeah, they are identical twins. You absolutely cannot tell the difference in looks, but personality wise you could. Kinda like Hikaru & Karou)

Illinois 

Peoria, settled in 1680 [incorporated in 1847] (1)

Naperville, 1831 [incorporated in 1845] (2)

Chicago, 1833 [3rd largest city too] (3)

Rockford, 1834 (4)

Aurora, 1834 [yeahhhh] (5)

Elgin, 1835 (6)

Springfield, 1839 (7)

Joliet, 1852 [suburb of Chicago] (8)