Local autonomy is a highly valued feature of good governance. The continuous attempts of many countries to strengthen the autonomy of local government shows the importance given to decentralisation and reinforcing competences at the lowest level of a state. This project1 is an extension and update of the “Self-rule index for local authorities in the EU, 1990-2014”, applying the comprehensive methodology to 57 countries over 30 years (1990-2020), including almost all EU, CoE and OECD member states. A network of experts on local government assessed the local autonomy of their respective countries based on a common code book, which has been updated to include more precise measures of local autonomy. We also collected supplementary data to better understand the determinants and implications of local autonomy. The eleven variables measured are located on seven dimensions and can be combined to a “Local Autonomy Index” (LAI). The data shows an increase of local autonomy between 1990 and 2020, especially in the Central and Eastern European countries. Countries with a high degree of local autonomy include the Nordic countries, Switzerland, France, Portugal and the USA.