In Southwestern Ontario during 1958, both exploratory and development drilling decreased slightly from that of 1957. During the year, 99 exploratory wells and 255 development wells were completed. Although there was a marked decline in activity on land, off-shore drilling on Lake Erie increased by more than 75% over the previous year. Natural gas production increased by 7% over 1957 to 15,500,000 MCF, and oil production increased 24% to 778,341 bbls., This is the highest since the year 1907, when more than 779,000 bbls. were produced. Six significant discoveries were made in the district during 1958, one each in Kent, Lambton, and Huron counties, and 3 off-shore in Lake Erie.

In the remainder of Eastern Canada (Quebec and the Maritime Provinces), activity continued at a high level. Eighteen exploratory wells were completed, a decrease from 27 in 1957, but total drilled footage was up slightly over the year. There was a marked shift in locus of exploratory activity from Quebec to the Maritime Provinces, particularly Prince Edward Island, but no oil or gas discoveries were made.