Cohabitation is an integral part of family research; however, little work examines cohabitation among teenagers or links between cohabitation and teenage childbearing. Drawing on the National Survey of Family Growth (2006–10), we examine family formation activities (i.e., cohabitation, marriage, and childbearing) of 3,945 15–19 year old women from the mid 1990s through 2010. One-third (34%) of teenagers cohabit, marry, or have a child. Teenage cohabitation and marriage are both positively associated with higher odds of having a child. The vast majority of single pregnant teenagers do not form a union before the birth of their child; only 22% cohabit and 5% marry. Yet most single pregnant teenagers eventually cohabit, 59% did so by the child’s third birthday and about 9% marry. Cohabitation is an important part of the landscape of the adolescent years, and many teenage mothers described as “single mothers” are actually in cohabiting relationships.