This paper uses data from the Panel Study of Income Dynamics to assess how the economic security and mobility of nonelderly adults in families with children has evolved from 1970 through 2005. We find that that for individuals in low-income families with a full-time, full-year worker, both economic security and upward mobility increased over time. Our findings underscore the importance of work for the long-term security and mobility of low-income families. The high and rising unemployment rates of 2009 clearly imperil the progress made during the last three decades of the 20th century.