Research has shown that learners do not always engage in appropriate metacognitive and self-regulatory processes while learning complex historical topics. However, little research exists to guide the design of technology-rich learning environments as metacognitive tools in history education. In order to address this issue, we designed a metacognitive tool using a bottom-up approach. Thirty-two undergraduate students read an historical narrative text either with or without the benefit of the metacognitive tool. Results from process and product data suggest that learners using the metacognitive tool had better recall and that the tool helped them (a) notice that particular events in an historical narrative text are unexplained, and (b) generate hypothetical causes to explain the occurrence of such events. We discuss the implications of these findings for the development of the MetaHistoReasoning Tool, a technology-rich learning environment that assist learners in terms of regulating their learning while they accomplish authentic tasks of historical inquiry.