The document discusses open government data portals and their evolution from initial publishing of data to supporting reuse and impact. It describes the key stages in developing portals, including the first portal launched over 13 years ago and the current European data portal. The document outlines work done to support the entire data value chain, analyze portal usage, develop guidelines to make portals more user-centric, and measure their effectiveness in promoting reuse. Examples are provided for how portals can better organize data, promote reuse, and co-locate documentation to support users.