- The commune of Pecq is located in a loop of the Seine. It is the only city, with Paris and Rouen, to be built on both banks of the river. It extends over 292 ha and its altitude ranges from 25 meters on the Seine to 97.65 meters in Vignes-Benettes. As of January 1, 2017, the city was home to 16,753 Alpicois, the name given to its inhabitants. It is part of the arrondissement of Saint-Germain-en-Laye and is the county seat of the canton.
- It was in the Middle Ages that the existence of the hamlet of Aupec appeared. Land of renowned vineyards, Le Pecq is mentioned for the first time in a charter of Childebert III, king of France, in 704. The abbey of Saint-Wandrille reigns over the estate, giving the city a religious past of first importance.
But it is to the presence of the Seine that the hamlet owes its rise. Many merchants, in order to avoid major tolls between Aupec and Paris, prefer to land their goods in this port and transport them by car to Paris. Port Aupec thus becomes a free port where it is possible to unload, store, handle, tranship the goods destined for Normandy and Burgundy, or from these provinces to supply the capital. Aupec settled down inns and merchants that housed and satisfied the current needs of a frequently renewed clientele. Even after the cancellation of the privilege of the water merchants of Paris in 1672, the port remained a great activity during twenty years. It was, in fact, one of the ports where the materials necessary for the construction of the Palace of Versailles were unloaded, and then the goods destined for the Court.
In 1595, Henry IV ordered the inhabitants of the Pecq to yield to him eighteen to twenty acres of land, necessary for the construction of the gardens of the Château Neuf de Saint-Germain. In compensation, he exempted the Alpicois from the size and various taxes, a privilege which they retained until the Revolution. It was thanks to the presence of the Sun King that the village developed between 1665 and 1682. Farmers and workers settled in Saint-Germain and the immediate vicinity to meet the various needs of the Court and to build the mansions that some sixty great lords have built in this city. It is estimated that at that time the population of the Pecq rose from 200 to 800 inhabitants.
- The delimitation of the commune of Pecq was carried out during the establishment of the cadastral plan in 1822. In 1875, following the subdivision of the grounds of Vésinet, a new commune was created. Le Pecq then lost a little more than half of the territory it owned on the right bank. Since the last modifications, the area of the commune is 292 hectares.
At the Restoration, Le Pecq became a very active trading port and was chosen as the terminus of the first French railway line, inaugurated on 24 August 1837 by Queen Marie-Amélie. The journey from Place de l'Europe to Paris (the Gare Saint-Lazare only dates from 1843) on the right bank of the Pecq (now Toyota garage) had lasted twenty-five minutes. The tourists flocked in, attracted by the charm of the village, the amenities of its shores and the presence of an important spa establishment, the "Spa Français" which operated until 1904.
- Parisians will spend a long weekend in the village and enjoy the pleasures of water 15 km from the capital. Beginning in 1878, a steamboat, a sort of boat with a dining room, provided daily service from May to September, between Pont-Royal in Paris and Le Pecq. This shuttle was abolished in 1925.
- Before the Second World War, Le Pecq was still only a village of 5,000 inhabitants whose houses were grouped on the left bank of the Seine. Part of its land was occupied by market gardens and orchards. Post-war reconstruction was to bring about a rapid change in the population: nearly 7,000 in 1955, 10,000 in 1960, more than 16,000 in 1970, a figure around which it has now stabilized.