https://thepointsguy.com/news/delta-...-a220-service/

Per Delta’s latest schedule update, here is the list of the carrier’s A220 routes that will roll out through early 2020 that shows the new west coast options:

Route___________________________________In-Service
New York (LGA) to Boston (BOS) _____________January 2019
New York (LGA) to Dallas-Ft. Worth (DFW)______January 2019
Detroit (DTW) to Dallas-Ft. Worth (DFW)_______March 2019
New York (LGA) to Houston (IAH)_____________April 2019
Salt Lake City (SLC) to Dallas-Ft. Worth (DFW)__May 2019
Seattle (SEA) to San Jose (SJC)______________June 2019
Minneapolis (MSP) to Dallas-Ft. Worth (DFW)____June 2019
Houston (IAH) to Detroit (DTW)______________July 2019
Houston (IAH) to Minneapolis (MSP)___________July 2019
Houston (IAH) to Salt Lake City (SLC)_________July 2019
New York (JFK) to Dallas-Ft. Worth (DFW)______August 2019
Los Angeles (LAX) to Austin (AUS)____________December 2019
Los Angeles (LAX) to Seattle (SEA)___________December 2019
San Francisco (SFO) to Salt Lake City (SLC)____January 2020
Seattle (SEA) to Salt Lake City (SLC)__________January 2020
Seattle (SEA) to San Francisco (SEA)_________January 2020

" full list of confirmed routes is here, and you’ll notice that most are medium-haul routes, around 900 miles or so, frequented by business travelers. These happen to be routes commonly served now by CRJ700, CRJ900 and Embraer 175 regional jets. Passengers used to sitting on one of today’s RJs are in for a major treat with the new jet."

I flew on it to DFW, really nice bird in the back...

Also:
https://thepointsguy.com/guides/delt...-where-to-sit/