On Monday, March 6, 1989, a very large and complex sunspot group, Region 5395, rotated into view around the east limb of the Sun and quickly gained attention when it produced an X15/3B flare (N35, E69). The event began a period of high solar activity that lasted two weeks and had many important consequences at Earth and in near‐Earth space. From March 6–19, Region 5395 produced 11 X‐class and 48 M‐class X ray flares. Prolonged proton events occurred that lasted several days and had an unusually high proportion of lower‐energy particles. The solar activity produced an historically “great” magnetic storm, long‐lasting Polar Cap Absorption events, and a major Forbush decrease, which is a decrease of the galactic cosmic ray flux observed at Earth. The ionosphere was greatly disturbed.