Inhabitants are called Saint-Germanois. With its elegant tree-lined streets it is one of the more affluent suburbs of Paris, combining both high-end leisure spots and exclusive residential neighborhoods (see the Golden Triangle of the Yvelines).
Saint-Germain-en-Laye is a sub-prefecture of the department. Because it includes the National Forest of Saint-Germain-en-Laye, it covers approximately , making it the largest commune in the Yvelines. It occupies a large loop of the Seine. Saint-Germain-en-Laye lies at one of the western termini of Line A of the RER.
In 1688, James II, King of England, exiled himself to the city due to religious conflicts in his own country. He spent the remainder of his days there, and died on 16 September 1701.
Prior to the French Revolution in 1789, it had been a royal town and the Château de Saint-Germain the residence of numerous French monarchs.
The old château was constructed in 1348 by King Charles V on the foundations of an old castle (château-fort) dating from 1238 in the time of Saint Louis. Francis I was responsible for its subsequent restoration. In 1862, Napoleon III set up the Musée des Antiquités Nationales in the erstwhile royal château. This museum has exhibits ranging from Paleolithic to Celtic times. The "Dame de Brassempouy" sculpted on a mammoth's ivory tusk around 23,000 years ago is the most famous exhibit in the museum.
Louis XIV was born in the château (the city's coat of arms consequently shows a cradle and the date of his birth), and established Saint-Germain-en-Laye as his principal residence from 1661 to 1681. Louis XIV turned over the château to James VII & II of Scotland and England after his exile from Britain after the Glorious Revolution in 1688. James lived in the Château for 13 years, and his daughter Louisa Maria Stuart was born in exile here in 1692. James II is buried in the Church of Saint-Germain.
The Treaty of Saint-Germain was signed in 1919 and was applied on July 16, 1920. The treaty officially registered the breakup of the Habsburg empire, which recognized the independence of Czechoslovakia, Poland, Hungary, and the Kingdom of the Serbs, Croats, and Slovenes (Yugoslavia).
In the 19th century, Napoleon I established his cavalry officers training school in the Château-Vieux.
During the occupation from 1940 to 1944, the town was the headquarters of the German Army .