Rohrer painted regularly
en plein air in the 1960s and 1970s, when his studio and home were in the
countryside in Christiana, Pennsylvania, close to his birthplace.
Like a nineteenth - century landscape painter, he usually works
en plein air, rendering one subject — say, a highway or some patch of Alpine
countryside — over and over until, in the artist's words, «it exhausts itself» or he runs out of paint.