Salas, a city councilman from Bakersfield, narrowly defeated Rios in the 32nd district representing a swath of the Central Valley from Hanford to Bakersfield. Salas defeated the GOP businessman by 2,503 votes, just shy of 52 percent of the vote.
The win moves Democrats closer to controlling 54 seats in the 80-member Assembly. That would give the party enough votes to approve tax increases and pass emergency legislation. The last time that happened was in 1978.
Democrats already gained two-thirds majority in the Senate.
Another key race remains too close to call. In Orange County, incumbent Republican Assemblyman Chris Norby was trailing Democratic challenger Sharon Quirk-Silva.