Okay, John has sent his list of additional species for the Lower 48, added to those on his online list that were originally from the Lower 48. His "official" number is 702, so here's the updated list:
US – Lower 48 Big Years - 680+
723 Olaf Danielson 2016
http://olafsbigyear.blogspot.com/
721 John Weigel 2016 personal communication
715 (+2) David McQuade 2019 personal communication
715 (+2) Tammy McQuade 2019 personal communication
706 (+1) Nicole Koeltzow 2018 eBird – US Lower 48 - 2018
704 Chris Hitt 2010 web page saved
704 Dan Gesualdo 2018 personal communication
703 Gaylee Dean 2019 eBird – US Lower 48 - 2019
702 Richard Dean 2019 eBird – US Lower 48 - 2019
702 John Weigel 2019 personal communication
699 Christian Hagenlocher 2016 ABA Listing Central
697 Laura Keene 2016 ABA Listing Central
692 John Vanderpoel 2011 ABA Listing Central
691 Neil Hayward 2013 ABA Listing Central
686 Brandon Reo 2015 eBird – US Lower 48 – 2015
686 Yve Morrell 2017 personal communication
685 Dan Sanders 2005 ABA Listing Central
683 Amanda Damin 2019 eBird – US Lower 48 - 2019
680 Dan Gesualdo 2015 eBird – US Lower 48 - 2015