Finding Websites From Company Name

I've got a list of 6,000 company names (along with their headquarters address) 开发者_Go百科and I need to find the web address for each of them. I'm considering using the Google Web API (obviously this will take a few days as only 1,000 queries per day are allowed) to do this(search for "COMPANY_NAME CITY STATE") and then take the first result. However I'm not 100% sure this will work, and I feel like there's a better way. I can do this in any language I know really, C++, Java, PHP, Python. This only has to be run once.

How would I use WHOIS to do this? I know how I would do it if I already knew the URL, but not the other way around(name to URL). And what would I do if it were privately registered?

BTW, these are US businesses.

You can use WHOIS instead of Google API for it.

Use Amazons Mechanical Turk. It's perfect for these kinds of tasks which can be hard to automate and typically need a person to validate them. It will cost a little but it should be manageable, depending on how bad you want the results.