The war left the mining industry in ruins again and the desertion of same by the American companies. Modernization of the nearly destroyed infrastructure began in the 1920s with the reconstruction of telephone lines and the construction of highways within the state. In the 1930s, a number of companies such as Cruz Azul Cement were expropriated and popular credit schemes such as the Banco de Credito Ejidal were created. Over 130 schools in rural areas were also built. Construction and modernization of infrastructure would continue through the rest of the 20th century.