What kind of board can span 16 ft for a wall pergola
Here is the answer to my actual question:

http://awc.org/codes-standards/calculators-software/spancalc

Edit: Sorry if I'm not on the same wavelengths as anyone else.  I already know about insurance and inspectors, and that was not at all what I was asking about.  I just wanted to know what length of wood would span a certain distance given various criteria.  I would have expected an answer to that question, instead of all the "your a dumb homeowner who's going to get in trouble" type replies.  I question the idea that there will be 50psf of weight from snow given the fact that it is an almost non-solid top, and saw no real attempt to answer my question, so I had to come up with this.  It took me awhile to find, and I hope it helps others.