Henry Jermyn, Earl of St. Albans (c. 1604-84), is commonly and on the whole rightly regarded as being more truly the 'founder' of London's West End than any other individual. It was he who was chiefly responsible for the first important development, in the years after the Restoration, of the area known as St. James's.

The highways at the southern and northern boundaries were probably both in existence in medieval times: that linking Charing Cross to St. James's Hospital (on the site of St. James's Palace) existed by the twelfth century, and the road later called Piccadilly also existed before the sixteenth century as the highway to Colnbrook and Reading. The Haymarket at the eastern and St. James's Street near the western boundary are both shown on a map of 1585: the latter street may have been formed in the reign of Henry VIII.