Friday Harbor is the only incorporated city on any of the 172 islands that make up the San Juan archipelago. It is located on San Juan, the second largest and the most populated of all of the islands. There are various ferries that take you and your car or semi truck from Anacortes to the islands. As a walk-on passenger, it is really straightforward to take the ferry. They seem to leave a few minutes passed the scheduled sail time, so you can basically get there with no time to spare, buy your tickets, and still have time to spare. (So I guess that means you gain time when you take the ferry?)
A salmon curing station was built on Friday Harbor in 1850. This was before the San Juan Islands became a part of the United States. Britain had their eyes on the archipelago as well, but after a little confrontation called the Pig War, the Canada-United States border skirts around the San Juan islands to the left instead of to the right.
Friday Harbor is full of architecture from the late 1800s to early 1900s, as well great restaurants, shops, and interesting art (inside galleries and antique stores and outside on the street). It is convenient to explore sans car since the ferry terminal drops you right off in town. We will be back in two days to see more of the island with a car. Which meant staking out the website at 7:00am two days before the sail date, spending a little more money on fares, and getting to the terminal sixty minutes before it departs instead of sixty seconds.