Mayfair is an affluent area in the West End of London towards the eastern edge of Hyde Park in Westminster, between Oxford Street, Regent Street, Piccadilly, and Park Lane. It was largely rural until the 18th century, and it became well-known for the annual "May Fair" held there from 1686 to 1784. Over the years, the fair became increasingly unpleasant and downmarket, so the Grosvenor family began to develop the land. Parks such as Berkeley Square and Grosvenor Square were surrounded by high-quality houses, and, by the end of the 18th century, most of Mayfair was built on with upper-class housing. It never lost its affluent status, and the decline of the aristocracy in the early 20th century led to Mayfair becoming more commercial, with many houses becoming major corporate headquarters or embassies.