Who Am I Really

My name is Robert Howard Cass Jr i'm from sacramento California. My grandfathers name is John Thomas Cass Jr or the third, i'm not too sure. I would honestly like to know who my ancestors are. My father and grandfather have passed away and I honestly don't know where to start looking. Would anyone do me a kind favor and point me in the right direction. I never realized the wide history of the Cass surname. It all is a little overwhelming to be honest. I would appreciate any and all helpful information. Thank you.