Complex sentence: Westminster Presbyterian was the first established on the site in 1891, it merged with Grosvenor Street Presbyterian in 1921 when the latter church's building was demolished as part of a plan to extend Bay Street.
Split into simpler sentences: Westminster Presbyterian was the first established on the site in 1891. It merged with Grosvenor Street Presbyterian in 1921 when the latter church's building was demolished as part of a plan to extend Bay Street.