From the heart of the city to the heart of the preserves. The true trailhead is more for neighborhood locals. Most hike portions of this loop starting at other trailheads. For those that want to check off 1A as complete... read on!
This hike starts at the end of Myrtle Ave. The park will tell you it starts at 16th Street and the canal. However, there's no parking at that location. It would also involve walking 16th Street and Myrtle Ave. I call those streets not trails. They have it starting there to link the preserves in with other county trail systems that won't be finished or used until I'm dead so let's go with the end of Myrtle Ave for now.
Start off switchbacking down a fenced corridor to the Myrtle Tunnel. Pass through the concrete jungle and a real trail exist on the flip side up a ramp. Albeit a real trail it's right beside a street, a neighborhood and well that hissing freeway fifty feet above you. About 0.5 mi heading north you leave the neighborhood and come to the Y of 1A loop.
Stay left for a clockwise loop. This also gets more of the undesirable out of the way. What you could hear before now comes into view. Bear in mind the freeway was kind of an afterthought. Planning dates back to 1955 as a spur to the I-10. Yet little surfaced(bad joke) until the mid 80's. It started out as a parkway from 1986 to 1991. Then was doomed by the massive valley growth to become a full fledged high speed hissing highway.
About 2.0 miles from Myrtle you approach the Dreamy Draw conglomerate of trails going everywhere. The 1A is the most signed trail in the preserves. Since there are several intersections without directions bring a map or a loaded GPS Route.
After a big Z switchback you are on the high northern ridge of the loop heading east. The city is still in the distance. Yet at this point the trail becomes peaceful leaving the hiss behind. You will pass a couple shortcut options. The first is the VOAZ 1B Trail. The second is called the Irregular Link. Past both of these the soil turns dark. It may not seem like much but with everything else in the preserves being white toned quartz it's a welcome sight.
Soon the loop takes you south towards the 304 Nature Trail. Here again you might have route finding issues if you're not familiar with the area. The 304 section doesn't even last a quarter mile then you are sharing trail with the 302 Circumference trail. This is the meanest climb of the loop. It's only 250 feet but it'll get your heart rate up.
From the saddle it's 1 mile through the tranquil valley to another saddle where you split away from the 302. Take the right which heads down quick into the biggest valley inside the city (that I know of anyhow). In the distance to the west you can just make out an old CCC stone structure. The trail misses it and goes above into the mountains overlooking the neighborhood. Even though it seems you should know the way a map still might come in handy.
Check out the Official Route and Triplogs.