 After the death of Ellen in 1957, the company was purchased by Frank Griswold, who ran the company in its purchased form until 1958, when he lost access to the American Monorail product line.On May 1, 1959, the Twin City Monorail Company was formed.In 1968, the assets of Twin City Monorail were sold to Dyson-Kissner Corporation, which operated Twin City Monorail until 1971, when they were acquired by Robbins & Myers.