Members of the Ramer family were not the only successful business owners in the 1800s. There was Abraham T. Moore and Son’s pump factory, Peter Milne’s Markham Mills, and John Monkhouse’s planing mill. David Byer founded a skin cancer treatment institute that evolved into the Byer Cancer Hospital at 300 Main Street North. In 1890, Aretus Urmy opened a general store at 266 Main Street North. A school was erected in 1835. A later school near the northwest corner of 16th Avenue and Main Street North was later converted for use as the Markham Museum.

The arrival of the Toronto and Nipissing Railway in 1871 began a major period of growth and many parcels of land were sold for new homes and businesses. Today, the southern part of Peter Street still contains many houses dating from the late 1800s.

In February 1907, Mount Joy became a police village. This was a form of municipal government created in the early 20th century for communities where the finances or population were not enough to create a village. A police village was not incorporated by the provincial government but by a by-law of the district or county government. It had its own elected governing body of trustees, which could establish fire and safety services and regulations, erect streetlights, and build sidewalks, but otherwise remained within the jurisdiction of the higher level of government.

Mount Joy was given over to the Village of Markham on January 27, 1915, with terms set by the Ontario Railway and Municipal Board. The Village of Markham was to supply Mount Joy with, “electric light for domestic use, street lighting and water.” Other provisions such as exempting Mount Joy from debts incurred by Markham, and holding the property assessment values for 10 years on agricultural property, were among other concessions and guarantees.