BAXTER STATE PARK, Maine (AP) — When Jackson Spencer set out to tackle the Appalachian Trail, he anticipated the solitude that only wilderness can bring — not a rolling, monthslong frat party. Shelters where he thought he could catch a good night's sleep while listening to the sounds of nature were instead filled with trash, graffiti and people who seemed more interested in partying all night, said Spencer, who finished the entire trail last month in just 99 days. At Maine's Baxter State Park, home to the trail's final summit on Mount Katahdin, officials say thru-hikers are flouting park rules by openly using drugs and drinking alcohol, camping where they aren't supposed to, and trying to pass their pets off as service dogs. Hundreds of miles away, misbehaving hikers contributed to a small Pennsylvania community's recent decision to shutter the sleeping quarters it had offered for decades in the basement of its municipal building. With last year's release of the movie "Wild," about a woman's journey on the Pacific Crest Trail, and what experts call a growing interest in outdoor activities, the number of people on the Appalachian Trail has exploded. [...] the numbers are only expected to climb further after "A Walk in the Woods" — a movie based on the 1998 Bill Bryson book about the Appalachian Trail— hits theaters this week.