We know that many people converted to Islam in colonial East Africa, but the why and how remain obscure. Recently, these Muslim congregations have come under scrutiny for producing Islamic radicals, but again the causes are poorly understood. This book traces the history of Muslim congregations in a mainland Tanzanian region from their inception in the early twentieth century to the early 2000s, using the records of governments and missions as well as hundreds of interviews. It argues that rural villagers became Muslim of their own initiative, in the pursuit of more equitable relations with Muslim townspeople and among themselves. The egalitarian ethos of these rural Muslims resonated with that of Tanzania's movement for independence, in which they strongly participated. The current conflicts among Muslims are rooted partly in their shifting and problematic relationship with successive post-independence governments, but also in the transitions in gender relations, education and ritual observance to which Islamization has contributed.