There is free tent camping (no RVs) at City Park just beyond the ball field, two miles south of the ferry on the water side of Zimovia Highway. The official limit is 24 hours, but this isn’t strictly enforced. Showers are available at a coin laundry near Chief Shakes Island [1], and at the high school swimming pool.
You’ll find additional camping at the city-run Shoemaker Bay Recreational Area (907/874-2444, year-round, RVs $25 with electricity, tents free), five miles south of Wrangell [2] and right alongside the highway. RVers get a pass to the city pool for showers and a free swim, and the area is near trails to Rainbow Falls and Shoemaker Overlook. The Forest Service’s free Nemo Campground is 14 miles south of town and up Forest Roads 16 and 6267; from here there are impressive views across Zimovia Strait.
Alaska Waters RV Park (241 Berger St., 907/874-2378 or 800/347-4462, www.alaskawaters.com [3], RVs $25) is on the south side of the harbor.
Links:
[1] http://www.moon.com/destinations/alaska/southeast-alaska/wrangell/sights/chief-shakes-island
[2] http://www.moon.com/destinations/alaska/southeast-alaska/wrangell
[3] http://www.alaskawaters.com