About 37 hours on amtrak
From the Amtrak app ... The Southwest Chief #3 Leaves Topeka at 1230 am (middle of the night) Arrives in Los Angeles at 800am the following day Travel time 33 hrs 30 minutes. Because of crew shortages due to covid the long runs to/from CA are not available early in the week right now, though the SW Chief may get back to seven days a week in a month or so.
Thanks! Your answer is awaiting moderation.