St Clair County Illinois

st. clair county once stretched from fort massac on the ohio river in a line northwest to the present site of peoria, followed the illinois river to the banks of the mighty mississippi and continued on to the ohio river at fort massac. the area was part of the northwest territory which was established by congress in 1787. arthur st. clair, became the governor of the northwest territory. two years later, st. clair paid a visit to what is now called southern illinois. on april 27, 1790 governor st. clair laid out the boundaries for the county which now bears his name. he established the county seat in cahokia. the photo to the right is the church of the holy family in cahokia. it is the oldest church west of the allegheny mountains. the church was established in 1699 by catholic missionaries from the seminary of quebec. by 1820, st. clair county had more than 5,000 residents; its population did not reach 10,000 until around 1835. after the civil war, there were more than 50,000 citizen