@danielswalk
Welcome!
Because of how frequently clients change companies, there is not a good way to keep a running list of which companies operate in which areas. To a degree, you just need to sign up for companies and you'll eventually have a few good hits. Make sure you are getting email notifications about jobs: A company that has nothing within in thousand miles of you today might pick up a new client tomorrow.
You can have a little bit of a jump start, however. At the bottom of this page, there is a link to over 200 companies. They are all legit - some are big, others are small. However, there is also a list of the "15 most discussed" companies. These are all larger companies with clients nationwide. I strongly suggest starting there. You will also notice that this forum is inundated with job advertisements. Read them. If there is something advertised in your area, sign up for the company - even if you are not interested in the job. They could have other work, too.
Finally, how far are you willing to travel? If you are willing to go 50, 100, 200 miles from home, you will find a lot more work - and often far more profitable work, sometimes with bonuses that more than compensate for driving time. On many days, I can't go more than 15 or 20 miles from home. However, there are some where I am off work and can drive over 200.
Hard work builds character and homework is good for your soul.