MacWhirter specialised in romantic landscapes with a great fondness for trees, spending much time in the hilly countryside of Perthshire. Initially, under the influence of John Everett Millais, he experimented with the detailed images of the Pre-Raphaelites, but later adopted a more sweeping style. With John Pettie he illustrated Wordsworths Poetry for the Young (Strahan, 1863). With Waller H. Paton and others, MacWhirter illustrated The Poetical Works of Edgar Allan Poe (Hislop, 1869).
MacWhirter specialised in romantic landscapes with a great fondness for trees, spending much time in the hilly countryside of Perthshire. Initially, under the influence of John Everett Millais, he experimented with the detailed images of the Pre-Raphaelites, but later adopted a more sweeping style. With John Pettie he illustrated Wordsworths Poetry for the Young (Strahan, 1863). With Waller H. Paton and others, MacWhirter illustrated The Poetical Works of Edgar Allan Poe (Hislop, 1869).