Since the 19th century, the number of doctors, hospitals, and medical organizations in and around Harley Street has greatly increased. Records show that there were around 20 doctors in 1860, 80 by 1900, and almost 200 by 1914. When the National Health Service was established in 1948, there were around 1,500. Today, there are more than 3,000 people employed in the Harley Street area, in clinics, medical and paramedical practices, and hospitals such as The London Clinic. It has been speculated that doctors were originally attracted to the area by the development of commodious housing and central proximity to the important railway stations of Paddington, Kings Cross, St Pancras, Euston and, later, Marylebone. The nearest Tube stations are Regent's Park and Oxford Circus.
Harley Street is owned by the de Walden family and managed by the de Walden Estate.
The Howard de Walden Estate dates from 1715 when Edward Harley, 2nd Earl of Oxford and Earl Mortimer, began the development of Cavendish Square in London, and the streets around it. This land had previously formed part of the Marylebone Estate of the Dukes of Newcastle. It had passed from Margaret Holles, née Cavendish, daughter of the 2nd Duke of Newcastle, to her daughter Henrietta Cavendish Harley. At the death of Henrietta's husband, Edward Harley, in 1741, this new Harley Estate passed to his only daughter, Margaret Cavendish Harley, who in 1734 had married William Bentinck, 2nd Duke of Portland. It was subsequently known as the Portland, and was handed down to successive Dukes of Portland. In 1879, the 5th Duke of Portland died without issue and his estates were divided between his sisters, according to the terms of the 4th Duke's will, and his cousin, who succeeded him as the sixth Duke. The Portland Estate eventually passed to the last surviving sister, Lucy Joan Ellis, who was the widow of the 6th Lord Howard de Walden, and has remained in this family since then.
Many famous people have lived or practised in Harley Street, including the Victorian prime minister William Ewart Gladstone, the artist J. M. W. Turner, and Lionel Logue, who successfully treated King George VI for his pronounced stuttering.
Queen's College, founded in 1848 and one of the oldest girls' schools in England, is situated on Harley Street.
- List of eponymous roads in London
- Macquarie Street, Sydney
- Rodney Street, the Harley Street of the North, in Liverpool
- Welbeck Street
- Wimpole Street