To understand the processes that lead to wealth accumulation and mobility, it is first useful to ask how much wealth mobility there is. The task of this chapter is to draw on both previous research and updated data to investigate this ambitious question. In a single chapter, it would be impossible to completely array all previous efforts to explore who the wealthy are and where they came from. To do this and to add new estimates of wealth mobility is probably much too large a goal. Yet, before attempting to explain wealth mobility in subsequent chapters, it is critical to first understand whether there is enough mobility to explain. Thus the aim of this chapter is twofold. First, I draw on research that has used a variety of different methods to study wealth mobility in the past, and I synthesize the information contained in this research to draw a complete picture of what we know about wealth accumulation and mobility. No one else, to date, has combined information found in in-depth studies of wealthy families, studies of social registers, and survey-based research in a coherent way. Second, I provide additional estimates of wealth mobility using multiple methods to explore patterns in the same data sets. The result is a more complete and robust portrait of the state of wealth mobility than was available previously.