The oldest Champagne House dates back to 1584, and is indeed Maison Gosset, formerly located in Aÿ, now in Epernay.....
"The history of the GOSSET family began over four centuries ago with the line's first official ancestor, Jean GOSSET (1484-1556), "Seigneur d'Aÿ et de Mareuil sur Aÿ". Sixteen generations of direct descendants would go on to distinguish themselves in Aÿ en Champagne as aldermen, mayors, public prosecutors, but above all in the cultivation of vines and the trading of Champagne wines. Whatever the era, the sole ambition of these men and women was to sublimate their terroir."
Read more about the history of the Maison de Champagne Gosset