First of all and this is very important...you have to mail each year separately! Or the IRS will miss one.
Where to mail federal paper returns
https://www.irs.gov/uac/where-to-file-paper-tax-returns-with-or-without-a-payment
See IRS publication 17 page 290 for where to file
https://www.irs.gov/pub/irs-pdf/p17.pdf#page292
