Sorry, I was responding to Tasha with kind of a reflex and didn't think to include info for the rest of you on what STP is!
So here goes:
Yep, the STP is an annual summer bike ride from Seattle to Portland, happening for almost 30 years now. It's considered a double century classic (actually 206 miles) and is put on by Seattle's Cascade Bicycle Club. Riders can choose to complete it in either 1 or 2 days. There is full support along the way, with official rest stops at 50 mile intervals and plenty of mini-stops all the way as well, also with plenty of overnight lodging/meal options at the halfway point for 2-day riders. It starts at the University of Washington early on Saturday AM, so that the finish line festival can be enjoyed in downtown Portland, OR either later on Saturday or all day Sunday. There are usually about 8,000 riders participating and the bike club has plenty of information online and in the form of prep/training workshops beforehand too, so there's no shortage of support and guidance for first-time riders. It's a lot of fun and is well-known in this area. Riders of all ages, shapes, and abilities participate - many have done it multiple times. I've done it for 5 years running and each year, I think I've gotten it out of my system, but have gotten hooked again for 1 reason or another!