Concordia Parish extends tall and narrow along the Mississippi River, where the ankle of Louisiana meets the instep. Almost one-third of its 20,000 residents live below the federal poverty line. Strip malls dominate Vidalia, the parish seat. Smaller satellite towns are home to Pentecostal mega-churches, defunct gas stations, and tin-sided shacks selling crawfish for $2 a pound. State highways run through low fields once flush with cotton that was picked by slaves and sold across the river to Natchez.