John Knox was born in Paisley. His early career as a landscape painter was spent at his studio in Glasgow, where he also taught. Among his pupils were Macnee, McCulloch and Leitch. In the late 1820s and early 1830s he lived in London and exhibited at the RA. He returned to Glasgow for a few years before settling at Keswick, where he spent the rest of his life.
Although it is not certain that John Knox was a pupil of Alexander Nasmyth (1758-1840), he is considered Nasmyth's closest successor in terms both of rural and urban imagery. Knox painted some fine panoramic views; his subjects included Lochs Lomond and Katrine and the west coast of Scotland.