I'm pretty sure if you ask any Seattleite that hikes, what the most popular hike around the area is and the answer will be: Rattlesnake Ledge. I think there are a few different reasons for this! But let me go back to my constant advice of starting your hike early. If you don't, you're going to have very little peace and quiet on this hike. It is a busy trail.
This hike is probably popular because it's hardly even an hour from the city. It's easily accessible, there is somewhat big area for people to park and there is a darn fine view at the top. Another reason it's popular is that it is a moderate difficulty level. People want to sweat! You'll definitely sweat a bit on this one. The elevation gain is almost 1200 feet, and the hike is 4 miles roundtrip.
A little paranoid advice from me: if you have a dog, please keep it on a tight leash at the top. There is a huge cliff. And there are tiny adorable chipmunks that run here and there, and I always envision a dog chasing a chipmunk, right off the edge. It's a scary thought.
I hope you bring a picnic to the top, because there is a huge area where you can relax after your hike, and enjoy your lunch. The view is pretty groovy! Trees and beautiful terrain as far as the eye can see. I feel so grateful to live in this area