What's the best option

So, I am basically making a venue/place search site. The only problem I have is with each place I want to add additional features / information that most Places API (like Google's Places API or FourSquare) doesn't provide. So, I was adding places by hand, than realized how stupid that must be since there are millions of places just alone in the United States.

Now, how should I go about this, because I want business owners to eventually be able to "claim" their venue and add information and media to it and the likes - which means I would most likely need all places added to a database correct?

Now, should I use a Places API like Google's or FourSquare to query and than populate the database? Or, is there a list / free resource where I can easily be able to populate the database? Also, does anyone know where these places actually find their information?

All help and info is appreciated.