This chapter provides historical overview of Condition C and strong crossover (SCO). These conceptions grew out of investigations into studies of conditions on backward pronominalization in English. Central to many of these investigations were developing notions of command (Ross 1967a; Langacker 1969; Culicover 1976; Lasnik 1976). The core idea of the Condition C account of SCO had been developed by Wasow (1972), who proposed reducing SCO to a condition on backward pronominalization. Wasow was revising and refining the account of Postal (1971), who first discussed crossover without distinguishing the weak and strong varieties. Alternative approaches to SCO were subsequently developed, as were attempts to extend the Condition C account to related domains. Some important problems for the Condition C account were raised by Higginbotham (1980; 1983) and Cable (2008).