WALLENSTEIN – Black migrants, some free, some formerly enslaved, cleared the land at the present-day border of Wellington County and Woolwich Township and farmed it in the early 19th century.But when the government surveyed and sold it in the 1840s, many of the 1,500 Black settlers couldn’t afford to stay on the very land they had cultivated.On Saturday, a new mural by Ottawa artist Kalkidan Assefa honouring that story was celebrated at Earthsca…