This is a list of all known remaining Griswold crossing signals in the state of Minnesota, excluding museums and private collections.
Updates and corrections welcome; last updated September, 2018.
In the Twin Cities, the Edina, Brookside / Yosemite Ave Griswolds were replaced sometime in 2014 or 2015; the St. Louis Park, Walker Street pair was replaced on April 23, 2015.
Minnesota Commercial's on Taft Street in Minneapolis came down in August, 2016. Their last set, in Minneapolis on Franklin Ave SE, was removed in the summer of 2017.
In outstate Minnesota, the Skally Line, Cliffs Erie, TCWR Granite, and ICE Owatonna signals are no longer in place; Hibbing and Faribault are the only known holdouts outside of MSP.
As of October, 2016, Hibbing still has 4 pairs of Griswolds, but, all of the rotating stop signs have been removed.
There are only half a dozen Griswold pairs remaining along active rail in Minnesota; four(!) in Hibbing, and one each in Minneapolis and Robbinsdale.
There are still a few holdouts along lines that are functionally dead; three along CP's unused MN&S/IC&E line in the South Metro and Faribault, and another on an unused UP spur in Plymouth.
There's not too much information online about extant Griswolds elsewhere, though of what's out there, Jerrold Crawford's page is probably the best (even though it hasn't been updated in ~15 years). He lists one at 1227 Old Bayshore Hwy, San Jose, CA, but Google Streetview shows it coming down between February 2009 and February 2011. Likewise, the pair at 2561 E D St, Tacoma, WA, disappeared sometime between July 2008 and July 2012.
South Dakota had one on the EE in Valley Springs on 487th Ave, though it was removed by August 2017 when I went to check on it myself.
Iowa had a few left along the former M&StL near Steamboat Rock as recently as 2014 (S 1st / State 56 Street in Steamboat Rock ;State 56 north of Steamboat Rock); aerial imagery confirms they've since been removed.
Wisconsin had one on an exempt stretch in Sheboygan at Union and Business, confirmed in place in June, 2017.
In April of 2018, I stumbled across this thread on rxsignals.com, which includes the following additional signals: