Recent protest movements brought attention to the one percent, a segment of the population that is critical to understanding inequality and social mobility but that attracts relatively little research attention. In this article, I survey current research on the one percent in the United States. I distinguish income from wealth and show that both are very concentrated but that the concentration of wealth, particularly financial wealth, is extremely high. I describe the demographic traits and finances of households who are in the one percent and discuss how these have changed in the past decade. I review literature that explains rising top incomes, and I propose that future research will usefully concentrate more on top wealth owners and on the demographic and life course processes that underlie income and wealth concentration. I conclude by speculating about why Americans are so tolerant of resource concentration. © Copyright ©2014 by Annual Reviews. All rights reserved.