37 miles, Multiple days
Santa Catalina is a beautiful island located only 22 miles off the coast of southern California. Though Catalina is a short 90-minute boat ride away, it feels like another world. There are two small, quaint towns on the island -- Avalon and Two Harbors -- and the remainder of the island is primarily wilderness managed by the Catalina Island Conservatory.
The 37.2 mile Trans-Catalina Trail traverses the entire island, from Avalon on the eastern tip to Starlight Beach on the western end. The trail begins and ends outside of town, so your total mileage is over 50 miles.
The Trans-Catalina Trail is relatively young, officially opening in April 2009. Most sections of the trail follow established trails or roads, but some sections are new and have rarely seen the bottom of a hiking boot.
Then length of the trail lends itself to hiking over four or five days. You must use established campgrounds, and the first day from Avalon to Black Jack is a long, grueling 15 mile hike. Because of the length of the first three segments and the steep hills and total vertical elevation gain, this is a very strenuous backpacking trip.
The ferry schedule will to some extent determine your itinerary. Not all ports on the mainland have service to both Avalon and Two Harbors.
If you choose to go in and out of Avalon, add in the expense of taking the Safari Bus from Two Harbors back to Avalon after you finish.
The best time to go is March or April. The weather is balmy, the hills are green and the wildflowers are in full bloom. The summer could get unbearably hot on the ridgeline trails. But this is southern California, so is there really a bad time to go?
There are bison. You may see them. They sometimes like to use the trails, too! Give them a wide berth and don't provoke them. Don't bother them, and they won't bother you.
Keep an eye out for bald eagles. Catalina is home to several nesting bald eagles.
Finally, if you've never used trekking poles before, you may want to seriously consider them for this trail. It is at times treacherously steep, and you'll be thankful to have a "portable handrail."