Longitudinal measures of income and poverty based on following the same people over time provide insights into the dynamic nature of economic well-being and mobility.  These longitudinal estimates allow policy makers, academic researchers, and the general public to paint a more detailed portrait of poverty than the one provided by more conventional measures that capture a snapshot of well-being at a single time period.  This paper describes poverty using measures with different time horizons and studies the frequency of transitions into and out of poverty in the United States.  It further examines how poverty dynamics vary across demographic groups.  The longitudinal poverty measures discussed include annual, episodic, and chronic poverty rates, as well as poverty entry and exit rates. These estimates are produced using data from the U.S. Census Bureau’s Survey of Income and Program Participation (SIPP).  The SIPP is a longitudinal survey which provides monthly data on family composition and economic well-being. The estimates in the paper cover the period of January 2013 to December 2014 from the 2014 Panel of the SIPP and the period of January 2011 to December 2012 from the 2008 Panel of the SIPP.