The Long Beach Peninsula is in the far southwest corner of Washington State, about 2 hours and 45 minutes by car from Portland, Oregon (the nearest airport with significant service) and around 3 hours from Seattle. The drive from Portland goes via Astoria, Oregon, crossing the Columbia River on the Astoria-Megler Bridge — at 4 miles, one of the longest continuous truss bridges in North America — and then north on Highway 101 up the peninsula.
There is no public transport to the peninsula worth mentioning. You need a car. From Seattle, the most direct route goes south on I-5 to Olympia, then west on Highway 12 and south on Highway 101 down the Washington coast. There is no air service to the peninsula itself.
Once on the peninsula, the main road runs its entire length — roughly 28 miles from Ilwaco at the south end to Oysterville in the north. Most services are in Long Beach town in the middle.