Reference

The date August 14, 1857, marks the formal inauguration of the "Nouveau Louvre" overseen by Emperor Napoleon III. This event was significant as it involved the inauguration of new buildings of the Louvre Palace, which were designed to complete the huge multi-building Louvre complex. These additions were critical to transforming the Louvre into the iconic structure it is today. The new buildings were primarily organized around what was then called Place Napoléon-III, later known as Square du Carrousel, contributing significantly to the Louvre's expansion and modernization during that period.

You can find more about this historical event on the Louvre Palace Wikipedia page.

Here is an image of the Louvre's North Wing, which was a part of the expansion: