I know what they are, but the closest we get hereabouts are the channel cats (aka "Blues", but they don't get as big up here). Half as long and a quarter the weight of a flathead. Anything over 20 lbs draws a crowd. The state record is just over 30#. In my pappy's time a 14' sturgeon was pulled out of nearby Cayuga Lake in a perch net (Cayuga's 35 miles long & 650 ft deep - our own Loch Ness). Two summers ago someone landed a 6 footer there and was smart enough to photograph it and return it to the water. BIG fine for killing one, but it sure would be a gas to hook into one.
Boy, those egg sinkers sure look like musket balls, eh? (Had to slip in a muzzleloading releted comment).