Conversation so far:
how far is dayton ohio from springfield ohio
There are 23.30 miles from Springfield to Dayton in southwest direction and 27 miles by car, following the I-70 route, 30 minutes far apart, if you drive non-stop.
does dayton ohio have any nicknames
Dayton, Ohio, is also known as The Gem City and the Birthplace of Aviation.

Question: why is the city called the gem city
Self-contained rewrite: why is dayton ohio called the gem city