Efforts to document mobility in the United States demonstrate that although there is considerable persistence in wealth ownership both intergenerationally and intragenerationally, upward mobility is relatively common. Efforts to explain who is mobile and why are even more rare than efforts to document mobility levels, but it is definitely possible to explain who moves up in the wealth distribution. New large-scale longitudinal data sets make this more possible than ever before. In Part Two of this book, beginning with this chapter, I explore the factors that affect wealth mobility. In particular, in this chapter, I isolate the effects of family background on wealth accumulation and mobility, emphasizing the role of such factors as inheritance, parents' achievement, and family size and structure during childhood. In the first sections of the chapter, I focus on the independent effect that these inputs have on adult wealth position. That is, I present separate estimates showing the relationship between parents' attainment and adult wealth, inheritance and adult wealth, siblings and adult wealth, and so on. I then present more complex models that incorporate multiple interacting effects that allow me to discuss the relative importance of the various factors that combine to produce adult wealth ownership. Figure 5.1 highlights the portion of the full conceptual model (Figure 4.1) that is the focus of this chapter and Chapter Six.