Proper database setup/import

Excuse my newbiness I am just learning Ruby/Rails.
What way would be correct or is there another way?

Lets say I have a single excel file of cities, counties, states that I
want to import into mysql for a Rails project.
Do I import each category (city, county, state) into separate tables
or all into one table? I guess I would need to know the proper way to
do this in order to create the has_many relationships. I also want to
maintain the relationships that exist in the excel file such as what
city is in what county.

Thanks in advance