2011 12 01 08 1043.4
2011 12 01 07 1043.3
2011 12 01 09 1043.2
2011 12 01 10 1043.2
2011 12 01 11 1043.1
1949 01 28 16 1043.0
1949 01 28 17 1043.0
1949 01 28 14 1042.7
2011 12 01 06 1042.6
1949 01 28 13 1042.3
1949 01 28 15 1042.3
1949 01 28 18 1042.3
1949 01 28 19 1042.3
1957 01 16 10 1042.3
1957 01 16 11 1042.3
Last night at midnight Sea-Tac hit 1043.4 hPa, smashing the old record of 1043.0 hPa.
According to the Weather Underground site the highest pressure in Seattle occurred on 12/3/1921 (1043.90 hPa), but that was at a very different location (downtown Seattle, not the airport) and thus not a fair comparison.
I hope someone contacts Ripley's Believe It or Not.