This chapter tells the story of Portland cement, from its invention in the tured mineral product. The success story of Portland cement is rooted in the unique combination of the abundance of its raw materials, the reactivity of the high-temperature clinker product toward water, and the properties of the calcium silicate and aluminate hydration products. Further development of Portland cements today mainly addresses the formidable challenge of reducing process CO2 emissions. Options include partial replacement of clinker by low-carbon resources, material-efficient use of cement and concrete products, and end-of-pipe carbon capture and storage or use.