He removed from Lebanon to Piqua, Ohio about 1820 and was the first regular professional lawyer who settled in the village.
He was receiver of public moneys and through his efforts a subsidy of 500,000 acres (2000 km2) of land was procured for building the Ohio Canal from Cincinnati to Lake Erie.
When his health began to fail, he retired from business and spent several months in Cuba hoping to derive benefit for his pulmonary disease by a change of climate.
His condition did not improve, and after returning to Cincinnati, he spent some time in revisiting several points in his old Congressional district.
William McLean died at his home in Cincinnati and was interred in the Catharine Street Burying Ground.