U.S. 101, the longest highway in California, starts in Los Angeles and meanders northward through Santa Barbara, San Francisco and into redwood country. For California's sparsely populated north coast -- the stretch of forests and farms and the smattering of towns that make up Humboldt and Del Norte counties -- 101 is a lifeline. It's the main artery for a region that was in economic trouble even before the Great Recession.

Just across the Humboldt County line, the highway bisects tiny Richardson Grove State Park, where it drops from four lanes to two and weaves through ancient redwood trees. The top speed is 35 miles per hour, along curves too tortuous for full-size commercial semis to navigate. The park is the one place along Highway 101 through which these trucks -- the kind that serve businesses across the United States, from mom-and-pop shops to big-box behemoths -- cannot legally travel, with a few exceptions.

Now, the California Department of Transportation (Caltrans) wants to improve and widen the highway. But locals are divided. Some see the restricted highway as a bottleneck obstructing economic development in a recession-racked community. To others, it's the finger in the dike forestalling a flood of development in a deliberately bucolic landscape. Both sides agree on one thing: Management of the highway through this state park has implications for development in the entire region the highway serves.

Verdant Humboldt County lies near the southern end of a temperate rainforest that once stretched from just north of San Francisco Bay to southern Alaska. The county's population density is among the lowest in California, and is concentrated around two hubs, Eureka and nearby Arcata. The woods form a largely pristine corridor from the inland hills to the rocky coast, creating a physical barrier from the more metropolitan south, and preserving the pastoral atmosphere that distinguishes the region. Locals call it the "Redwood Curtain."

To get through the two-lane section of Highway 101 through Richardson Grove, loads have to be transferred onto smaller trucks or detour into Oregon before heading back south, increasing the trip between Oakland and Eureka, for example, by 446 miles. A 2008 state-commissioned study found that the restriction increases trucking costs by 16.9 percent for affected industries, including timber, manufacturing, floral and brewing, resulting in an annual income loss of $8 million for businesses and residents in Humboldt and Del Norte counties.

The restriction stems from the Surface Transportation Assistance Act (STAA) of 1982, a Reagan-supported law that, among other things, standardized the length of semi-trailers at a maximum of 53 feet. STAA semis aren't allowed through Richardson Grove because the route is so curvy, and they're so long, they can't turn without "off-tracking" -- making use of the opposing lane or the highway's shoulder. Off-tracking on the narrow, two-lane highway endangers both motorists and the trees that line the road. Before 1982, smaller, 40-foot trailers were more common, and though STAA-sized semis may have traversed the park at times, it would have been infrequent.

Humboldt County's 2008 Regional Transportation Plan blamed STAA limits for "preventing (the county's) businesses from being profitable and competitive with other similar business along the west coast." Caltrans' $5.5 million improvement project will, theoretically, level the playing field by creating an uninterrupted freight corridor from L.A. to Oregon. Construction would widen some shoulders and adjust lane alignment to allow semis through. Thirty trees in the park would be cut down -- only two redwoods, neither of them old-growth. Excavation will take place around the root systems of 86 more trees, including old-growth redwoods. The project is set to break ground this September.

When Eureka resident Trisha Lotus heard about the plan, she, like many locals, took it personally. Born in 1949, Lotus spent much of her youth behind the Redwood Curtain, summering in cabins among the big trees, and swimming in creeks and rivers.

Around the turn of the last century, Lotus' great-grandfather, Henry M. Devoy, owned a tract of old-growth redwoods in Humboldt. In 1922, 120 acres were turned over to the state, then under the leadership of Gov. Friend W. Richardson. This land became Richardson Grove State Park.

When Devoy owned the property, a horse path cut through it, crossing creeks, washes and the South Fork of the Eel River. In 1915, the trail was converted into an all-weather road, and in the 1930s, Depression-era stimulus programs put people to work constructing bridges. The one-time horse path is part of today's Highway 101. The park, meanwhile, has grown to more than 2,000 acres, with hiking, camping, salmon fishing, some of the last ancient redwoods, and that uniquely 21st-century amenity: wireless Internet.