I second this. Make sure you stop by the "smaller" yards, too. I originally checked out the big box stores (Lowes, Home Depot) around me, which had lumber that might be alright for building a ramshackle shed or for kindling, but nothing else.

There's an independent home building supplier local to upstate NY that I checked out, expecting to find nothing. Instead, every time I go up, I've found beautiful clear western red cedar 2x4's for paddle blanks. They've even got 16' lengths of 1x2 pine that I could use for gunwales and stringers (albeit, with a bit of pawing through to remove the biggest knots).

Look for lumber mills, too. There's a few local here that I'll be bothering once I get around to needing air-dried or "on the greenish side" wood for laminated coamings.