Answer:
It's large size, which made it difficult for the Union to conquer.
I believe it was in Chicago
A renewable source is one that can be renewed.
Some examples are solar energy, biomass and wave energy
They were both from Poland and they both fought in US Independence War. Kościuszko was fighting more in norther part of US, he was famous for building forts. Pułaski fought more on south US, he created first American cavalry. They are still national heroes in Poland.