Accountability is one of the cornerstones of good governance. Establishing accountable governments is a top priority on the international development agenda. Yet, scholars and democracy practitioners know little about how accountability mechanisms develop and thus can be supported by international and national actors. The present study tackles the questions of how, and in what sequence accountability sub-types develop. We consider not only vertical (elections and political parties) and horizontal accountability (legislature, judiciary, and other oversight bodies) but also diagonal accountability (civil society and media) in both their de-jure and the de-facto dimensions. By utilizing novel sequencing methods, we study their sequential relationships in 173 countries from 1900 to the present with data from the new V-Dem dataset. Considering the long-term dimensions of institution building, this study indicates that most aspects of de-facto vertical accountability precede other forms of accountability. Effective institutions of horizontal accountability—such as vigorous parliaments and independent high courts—evolve rather late in the sequence and build on progress in many other areas.