Christophe Stahl described one route on Mt Wilson:
This out and back route to Mount Wilson from Sierra Madre, CA starts at one of three trailheads located in the cities on the south side and is also the shortest one. There are however some variations possible when starting from this trailhead by going through Jones Peak and / or Mount Yale and Mount Harvard. All variations are about the same distance. This route is also what seems to be the most popular to go up. Parking is fairly easy close by Lizzie’s Trail Inn at 167 E Mira Monte Ave, Sierra Madre, CA 91024. No parking on the streets there between 2am and 5am though.
From the corner of Lizzie's Trail Inn go up the paved road one block to reach the trailhead. Take the Mount Wilson trail on the left. At the first intersection you can make a left to Jones Peak as a possible variation. The route for this FKT is going straight there. There are signs at almost every intersection so there are less chances to get lost. At the next intersection stay on the left. There is a short trail that goes down to a place called First Water. At the following intersection, again, go straight. The trail on the left is another access to reach Mount Yale and Mount Harvard. Around mile 4.5 where Mount Wilson trail crosses the Firebreak, a larger trail, at an intersection with a couple of benches, make a left to continue going up. Make sure to respect the signs there to stay on the trail. You will soon reach a Jeep trail called Mount Wilson Road that you can follow all the way to the top to Mount Wilson with all its antennas. At the first intersection on Mount Wilson Road, right after the single building on the left, there is a trail on the right you can take to reach the south end of the Mount Wilson parking lot. This FKT route makes a small loop in this area, taking that 1.4 mile Mount Wilson Road all the way to the top before reaching the Cosmic Cafe and going down that short trail.
Going back to the starting point, there is again an opportunity for a variation through Mount Harvard and Mount Yale. With this FKT route, on the way back make sure not to miss the Mount Wilson trail by the benches since there are 3 trails going pretty much the same direction. The correct trail is a bit hidden below the larger trail on the far right. Half way from this point there is again a possible variation by going through Jones Peak, but this time it means you will have to go up 1 mile instead of following the way down. This route is about 16 miles long with an elevation gain of about 4,900 ft. There is access to bathroom and water at the top, but the free water there does not taste anything like fresh spring water. If you need any, you might want to spend a few bucks at the Cosmic Cafe. Last piece of advice is that this narrow trail was pretty busy on a Sunday morning and must be much better to take on a week day.