Mr. Selfridge, the Wisconsin-born retailer   who left school at 14, rose to become a partner in Marshall Field's. Chicago. Founded in 1852, it was one of the first and most ambitious US department scores. Mr. Selfridge had done well with Marshall Field's. He liked to say, "The customer is always right," which made the Chicago store popular. And he is believed to have invented the phrase "Only [so many] Shopping Days until Christmas". When he visited London on holiday in 1906 he was surprised to find most of the city's department stores were no match of their American and Parisian competitors. This led Selfridge to leave the US and establish Selfridges. a department store named after him. at the west end of London's Oxford Street. In Oxford Street, Selfridge's design team shaped an ambitious classical palacc building with a wall of plate glass windows. Opened in 1909, Selfridges offered customers a hundred departments along with restaurants, a roof garden, reading and writing rooms, reception areas for foreign visitors, a first aid room and. most importantly, a small army of knowledgeable floor-walking assistants who served as guides as well as being thoroughly instructed in the art of making a sale. Mr. Selfridge did much to make the department store a destination rather than just a big and comprehensively stocked city shop. It became a place to meet and for ladies to lunch. Mr. Selfridge later introduced the department store as a key element of the 20th Century culture, and Chaplin acknowledged the growing trend for shopping in the department store in his film The Floorwalker. What is the main purpose of the article?
To introduce the history of Selfridge . To compare different department stores. To encourage readers to spend more. To explain how to start a department store.