BLY, Ore. — This hard-knocks hamlet seems an unlikely place to search for clues to the al-Qaida terrorist network. It sits on an arid plateau in Southern Oregon, about 50 miles east of Klamath Falls. With a population of about 250, it has a couple of cafes and small stores, an antique shop, and the razed foundation of an abandoned lumber mill. But in late 1999, federal authorities and other sources say, the area had something far more unusual: militant Muslims scouting a ranch outside of town as a possible training camp for jihad fighters. That aborted effort has now...