A recruiter for Union Pacific Corp., she has openings to fill, the kind that sometimes seem to have all but vanished: secure, well-paying jobs with good benefits that don't require a college degree.

But they require specialized skills—expertise in short supply even with the unemployment rate at 9%. Which is why on a recent morning the recruiter found herself in a hiring hall here anxiously awaiting the arrival of just two people she had invited to interviews, winnowed from an initial group ...