Broad demographic shifts in marital status, educational attainment and employment have transformed the way young adults in the U.S. are living. This Pew Research Center analysis of census data highlights the implications of these changes for the most basic element of their lives -- where they call home. In 2014, for the first time in more than 130 years, adults ages 18 to 34 were slightly more likely to be living in their parents' home than they were to be living with a spouse or partner in their own household. This turn of events is fueled primarily by the dramatic drop in the share of young Americans who are choosing to settle down romantically before age 35. The median age of first marriage has risen steadily for decades. In addition, a growing share of young adults may be eschewing marriage altogether. A previous Pew Research Center analysis projected that as many as one-in-four of today's young adults may never marry. While cohabitation has been on the rise, the overall share of young adults either married or living with an unmarried partner has substantially fallen since 1990. This report presents the historical trends in the share of young adults who live with their parent(s). The first section presents a simple classification of living arrangements. The second section examines trends in living with parents by demographic and geographic groups. The third section explores the shift away from living with a romantic partner and toward living with parents. The final section examines the relationship between living with parents and trends in the labor market opportunities of young adults. Other key findings include: (1) The growing tendency of young adults to live with parents predates the Great Recession.; (2) In 2014, 40% of 18- to 34-year-olds who had not completed high school lived with parent(s), the highest rate observed since the 1940 Census when information on educational attainment was first collected; (3) Young adults in states in the South Atlantic, West South Central and Pacific United States have recently experienced the highest rates on record of living with parent(s); (4) With few exceptions, since 1880 young men across all races and ethnicities have been more likely than young women to live in the home of their parent(s); and (5) The changing demographic characteristics of young adults--age, racial and ethnic diversity, rising college enrollment--explain little of the increase in living with parent(s). (This report was written with assistance from: Richard Fry, Kim Parker, Claudia Deane, Renee Stepler, Eileen Patten, Michael Keegan, and Marcia Kramer.)