Personally, I would look to arrive at the airport just after 10am (and leave DLR around 9:30am), but under this scenario:
1) Southwest, which boards at approximately 11am.
2) I have PreCheck
3) No kids to wrangle/no bags to check
If I had to return a rental car, wrangle kids and check-in bags, and if the "worst case scenario" of missing the flight is problematic (that is, maybe it was the only flight to Chicago that day, and not one of the many hourly flights to northern california), I'd try to arrive at 9:30am just to be on the safe side. That would mean leaving DLR around 9am.
If this is a workday (M-F), the commute direction is southbound 5/55/405, but 9am should still be okay. Turn on Waze and kind of play it by ear that morning.
ETA: I legitimately thought this was a thread about flying from DCA (Reagan National) to SNA (John Wayne), and thought it was cool both are named after California actors of another era, lol.