He was born in Bramley, Yorkshire[1] and educated at Leeds Grammar School.

In 1859 Johnson became Acting Locomotive Superintendent at the Manchester, Sheffield and Lincolnshire Railway.

In 1864 he was appointed Locomotive Superintendent of the Edinburgh and Glasgow Railway.

In 1866, after only two years in Scotland he replaced Robert Sinclair of the Great Eastern Railway (GER) at Stratford Works.

S. W. Johnson's father, James Johnson, worked for the Great Northern Railway (GNR) for sixteen years before becoming engineer of the North Staffordshire Railway (NSR).