The LaCroix Foundation was an organization run by Prince Sebastian LaCroix.
The LaCroix Foundation seemingly owned the Venture Tower building, as there were two prominent "LaCroix" signs in the lobby. There were, however, other tenants of the building. The Foundation's offices were spread throughout the Tower: there were offices and a meeting room at the 14th floor, a vaulted chamber used by his Sheriff on the 55th floor, and the prince's personal offices at the penthouse.
It's not known what the Foundation did other than act as a holding company for the Venture Tower.