The ancient parish comprised the township of Cefn Post, in Merioneth, and the townships of Maes yr Odyn, Llysan, and Cysilog (or Llysyllog) in Denbighshire.
The church, which is dedicated to St. Michael, was mentioned in the Norwich Taxation of 1254. It was partly rebuilt in 1853; and was restored in 1901/1902.
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For family history information about the church and parish, visit the GENUKI Llanfihangel Glyn Myfyr page.