On October 18, 1985, moderate geomagnetic activity (Kp = 4+) near 1200 UT was followed by observations of a large-scale traveling ionospheric disturbance (TID) at observatories in Greenland, eastern North America, and Europe. Estimates of the speed and direction of the TID indicate that it was caused by an atmospheric gravity wave expanding from a localized source over the Arctic Ocean north of eastern Siberia. Auroral imaging shows that the source region was located near the westward edge of an expanding auroral bulge and may have been associated with a westward traveling surge (WTS). The largest TID amplitudes were observed along a line perpendicular to the orientation of the auroral oval, and TID periods increased with distance from the source region. This set of observations provides one of the most complete cause and effect relationships found thus far in the study of atmospheric gravity waves.