Good news! A partial index of St Mary's census for 1911 is now online at AllCensusRecords.com
A word of explanation -- St Marys Perth County 1911 census consists of 4 subdistricts:
Subdistrict 34 - 18 pages
Subdistrict 35 - 18 pages
Subdistrict 36 - 16 pages
Subdistrict 37 - 18 pages
Subdistrict 34 has a head of house index for pages 1-12. 13-18 are not yet complete
Subdistrict 35 is not transcribed yet
Subdistricts 36 and 37 are completed and have an every surname index.
Head of Household Index for St Marys, Perth Co. Ontario 1911 Census for Subdistrict 34, pages 1-12
Every Surname Index for St Marys, Perth Co. Ontario 1911 Census for Subdistrict 36 & 37 all pages
Good luck, hope you find an ancestor or two!
Feel free to forward this email to interested mailing lists .