I've seen it coded as both "Bombardier CRJ-900" and "CR9" thus far. In any event, if you see "Canadair" or just plain "CRJ," you're unfortunately stuck on the 50-seater.

While ~900 miles on a CRJ isn't the most fun, a quick scan of likely/frequent offenders on the NW schedule revealed 7 CRJ flights over 1,000 miles (could be even more). The longest one I found was MSP-SAV at 1,092. The others I saw (longest to shortest): MSP-CHS, MSP-MYR, MSP-ORF, DSM-LGA, MSP-HPN, IND-FLL.

For what it's worth, though some people find the ERJ better than the CRJ, CO has their ERJ's deployed on much longer routes than NW does the CRJ's. A glance through the CO schedule found 8 ERJ routes over 1,200 miles, with the longest one being EWR-OKC at 1,325 miles. Some are also on routes where you'd generally expect all mainline equipment, such as IAH-YYZ and IAH-DCA.