Mexico City, 1968 was the first games to use a synthetic track. Before that, cinder tracks were used. The first few Modern Olympics saw their Track and Field events run on the grass.
Times were tough for Paris in 1900 and they didn’t want to spend much on their Olympics. They held the Track and Field events in the Bois (woods) de Boulogne on an area of grass because they didn’t want to build a cinder track! They refused to cut trees down and both javelins and discuss were hitting and getting stuck in them. They used the River Seine for the swimming events and when the current was running fast, world records tumbled!