Arcata is 270 miles north of San Francisco — a four-to-five hour drive on US-101, which runs right through town. The highway is scenic but slow in places; there are no freeways for most of the distance north of Cloverdale. The drive is worth doing at least once for the redwood corridor and the coastal stretches near the Lost Coast turnoff.
By air: Arcata-Eureka Airport (ACV), also called California Redwood Coast-Humboldt County Airport, is 8 miles north of Arcata in McKinleyville. United Airlines operates daily connections to San Francisco and Los Angeles, with a few other seasonal routes. The airport is small; flights are priced unevenly, and it's worth checking whether driving from Sacramento or flying into SFO and renting a car makes financial sense for your trip.
By bus: Redwood Transit System and Greyhound provide bus connections along the US-101 corridor. Greyhound connects Arcata to San Francisco with one daily service (roughly 6 hours). The Arcata Transit Center on K Street is the arrival and transfer point for most regional services.