October 19, 1935 Earthquake: Helena, Montana, United States

This is the main earthquake of the 1935 series of shocks at Helena. Two people were killed by falling bricks, several were injured, and property damage was estimated at about $3 million. The earthquake damaged agout 300 buildings, of which more than 200 lost their chimneys. Damage was most severe in old 2 and 2 1/2 story brick houses on alluvial soil in northeast Helena, but severe damage also occurred in the southern business section of Helena. Downed chimneys and cracked plaster were common throughout the city, and in sections, almost all chimneys were destroyed. Gables commonly were damaged, regardless of the structural material used or the location of the builidng. Changes in the volume of flow of many wells and springs occurred. The most noted change was an increase in flow of springs or the formation of new springs. Seven Mile Creek, which was almost dry before the earthquake, was about 1.5 m wide and 30 to 45 cm deep when it was observed on Oct. 31.

The earthquake was also felt in parts of Idaho, Washington, Wyoming, and in adjacent areas of Canada.

(above from Reference #542)

Reference #1250 lists $19 million damage.