Stamen Maps Terrain. These are high-contrast Black and White maps. Four billion of them.
These are not updated from OpenStreetMap very often data several years old 1 but they have proven longevity and are used by a lot of web maps. Missed this one from last month. Open source terrain maps.
The Knight grant also funded.
Four billion of them. Active 4 years 6 months ago. Until recently Mapquest provided the de-facto standard for open tile access for OpenStreetMap data. Assemble a selection of different map layers like backgrounds satellite imagery terrain roads or labels.
