Sean O'Brien 50k is a hell of a race. I loved it. It was hard and the hills try to kick your ass. The atmosphere is electric. The people running are incredible. I am so happy I ran it.

The start times are varied depending on your race with 100k/50m starting earlier and the 50k and marathon starting together later. Either way, you start before the sun is truly up before it's really warm...which makes it an interesting race. 30s at the start, 70s/80 at the finish (that's California winters for you!). Parking is fine, if a little far away for the later start times. BRING CASH to pay for it!

The out and back course itself was AWESOME. It's a mix of single track, fire road, hills and rolling hills. It's open to the public, which leaves it clear of hikers in the morning but you may get some around midpoint. After a little downhill, the start is mostly grueling up, which means you finish on the downhill. There's a river crossing in the first couple miles, chilly but not gushing at the start and awesome to cool off in on the way back.

The aid stations were nicely situated (I'm pretty sure there were 3 that you hit twice) and really wondrously stocked with snacks, electrolyte drinks, water, energy chews, etc. Beyond that, I'm positive this race has the BEST VOLUNTEERS of any race I've ever run. They really look out for you and provide a smile and spark of enthusiasm that you need. Also, to deal with that temperature jump, everyone 50k and up can do a drop bag which you get at I think mile 13. Thank goodness! I went from long sleeve to tank top.

The finish line felt like a picnic! I stayed all day after I was done, hanging out, snacking, and watching the other runners come in.

I highly recommend this as a challenging 50k with an unbeatable atmosphere.