Shoreline Trail is just a lovely ramble along the side of the bay in one of the rare places where it is little changed from the days of the Miwok. North San Pedro Road is never far away, but the terrain usually screens off its light low speed traffic. The trail runs mostly through mixed woods or across grassy slopes, where birds and wildlife may be encountered and wildflowers must be fine in spring. It starts along the edge of a wide tidal marsh and follows the coast to the south edge of the park. In the last half mile or so, you cross a low ridge in interesting chaparral and get a nice view west over San Rafael to Mt. Tamalpais. And/or take the short connector “Village Trail” down to China Camp Village, where there’s an interesting museum and a beach in case you’re ready for a swim. Also a nice picnic area, one of several you will have passed, most with accessible flush toilets.
I started from Back Ranch Campground since it has bus service to within a mile or so, and that end of the trail is designated as wheelchair accessible for the first mile, but you could also start from Miwok Meadows, Bullhead Flat or China Camp Village.
In that first “accessible” mile the trail wanders out from the campground, crosses grassy slopes with views over the marsh and San Pablo Bay, runs close to the road for a bit, then up a ravine under oak, bay and madrone trees, across a little bridge and back down, passing Miwok Meadows Day Use Area. The surfacing is smooth fine gravel which would be fine even after heavy rain, and the occasional slopes are only slightly over the ADA’s 1/12. But this very appealing stretch of trail has an important drawback, shown in one photo: in several places where erosion has been a problem, they've laid large uneven cobblestones which give any wheelchair a jolting workout, hard on chair and rider. Most of these spots are less than ten feet long, but the one shown is twice that, and rough.
South of Miwok Meadows is another story, with a couple of narrow spots I wouldn’t have crossed without trustworthy help.The ups and downs are modest, and well designed switchbacks make them comfortable for most users, though the rock trailbed and occasional roots give uncomfortable going for a wheelchair in many places. I thought it was worth the rough ride, but your results may vary!
Details: Non-service dogs are not permitted on the trails; bikes are, and are frequent. There is a parking fee charged in the campground and picnic areas. In case you want to start at Miwok Meadows, note that the parking lot there is closed to the public, and San Pedro Road's shoulder at that point is a bit narrow. Also the supposedly accessible toilet at that picnic area has no grab bars. There are (backless) benches along China Camp's trails, but due to steep hillsides some are placed up or down from the trail where, if you need one, it may be hard to get to.