This paper reviews the recent changes in labor force participation and withdrawal in the United States and examines some of possible reasons for the changes. Nowadays, many older Americans are extending their work lives and delaying retirement. This longer work life is accompanied by the emergence of new patterns of retirement, such as gradual retirement, phrased retirement, and un-retirement. Generally, highly-educated, male workers and divorced urban women tend to continue working past traditional retirement age. Significant social, demographic, and economic changes have contributed to the trend toward continued labor force participation and later retirement. Greater life expectancy and improved health status enable older workers to extend their working lives. Some older Americans choose to work longer due to policy changes such as the elimination of mandatory retirement, work incentives provided in the Social Security, the shift to defined-contribution pension plans, and the erosion of retiree health insurance along with economic recessions. Finally, the paper discusses the potential health benefits linked with extended working lives and the challenges faced by older workers, especially those with socioeconomic disadvantages.