Taxis are sometimes in short supply in Wrangell, so it's very common for visitors to walk along Evergreen Avenue to reach Petroglyph Beach State Historic Site. This beach has the highest concentration of petroglyphs in Southeast Alaska, scattered openly on the beach where you are free to wander and discover them. The site itself is at least 8,000 years old.
Try to time your visit with a reasonably low tide, so there's more room to wander; and please don't take souvenir rubbings from the petroglyphs, because that wears them down. There are replicas near the park entrance that you can use for rubbings if you like.
Although Evergreen Avenue is a main road in Wrangell, the community is small enough that traffic is relatively light, and drivers are usually very courteous about walkers alongside the road. Make sure to wave or otherwise acknowledge their presence — that's a basic courtesy here.