Credit cards are used by every segment of our society, from college students to retirees, from the unemployed to hopeful entrepreneurs, from some of the poorest households to the wealthiest, and across all race, sex, and ethnic groups. This study documents the growth in credit cards as a method of paying for and financing purchases in the United States, and the diffusion of credit cards through almost all segments of the American public. Using data collected by the Federal Reserve Board in its Survey of Consumer Finances, this paper focuses on the period from 1970 (four years after the introduction of what are now Visa and MasterCard) to 2001 (the most recent year for which the Survey of Consumer Finance data are available). About 73 percent of all households had at least one credit card in 2001, up from 16 percent in 1970. And households use these cards more than they used to: the average household that had at least one credit card charged $720 a month in 2001 compared with $136 in 1970 (both in 2002 dollars). Households also use credit cards more as a source of financing. Between 1970 and 2001, there was an eight-fold increase in the dollar value of credit-card debt held by the average U.S. household. Credit cards have displaced store cards and installment loans as a source of financing.Credit cards have become increasingly available and are used more by most segments of society. Disadvantaged groups, in particular, have experienced high growth in credit card access and use. For example, in 1970, 2 percent of all low-income households owned credit cards. By 2001, more than one third did. In fact, by 2001 credit cards on average accounted for over 45 percent of low-income households' non-mortgage debt. Another traditionally disadvantaged group, single women, has also gained increased access to credit through credit cards. More than 60 percent of all single women without children have credit cards, while over 50 percent of single women with children own cards - and most carry balances on those cards.Over the last thirty years, virtually all demographic groups have increased their ownership and use of credit cards. Credit cards have become an indispensable means for Americans and consumers worldwide to make safe, convenient payment transactions. More importantly, credit cards have helped households to obtain credit that, certainly for the less wealthy, may not have been available otherwise.