Born in Pennsylvania, Knight spent most of his life as an American expatriate working abroad in Paris. After studying at the Pennsylvania Academy of Fine Arts, he moved to Paris to study at the E´cole des Beaux Arts in 1861. There he had the unique opportunity to work with many celebrated artists including Pierre Auguste Renoir, Alfred Sisley and Charles Gleyre.

In 1863, Knight returned to Philadelphia to fight with Union soldiers during the Civil War. He sketched battle scenes to create a personal, historical account of the war. Knight returned to Paris in 1871 and began studying under realist painter Jean-Louis-Ernest Meissonier, whose enormous influence on the American artist helped Knight obtain entry to the prestigious Paris Salon.

By the mid-1890s, Knight had established his home in Rolleboise, a charming village on the Seine that became the subject matter for the majority of his works. In his quest to faithfully portray the light of the sun and moon on its environment, Knight built himself a glass studio in his garden where he could paint in natural light, regardless of the weather. Knight exhibited his works extensively including the Paris Salon, the Munich Salon and world exhibitions, earning a number of awards and medals. His paintings are highly collectible and are represented in a number of private and museum collections.