The engineers in Louisiana were military men, either those who held diplomas, having completed the necessary theoretical and practical studies, or officers who had been promoted to "engineer". Along with the Jesuit priests, the high-ranking officers, the governor and certain concessionaires, they constituted whatever elite there was in the colony. Their skills, honed in the king's armies in the east or in the Pyrenees, had to be adapted to the tropical conditions of Lower Louisiana and to the materials that could be found or made there: cypress wood, oyster shell lime and bricks of variable quality.
Mission orders given to chief engineer Louis Pierre Le Blond de Latour, November 8, 1719 CAOM, B42bis, f° 311

Thus, the buildings that were put up in a matter of days or weeks in the early days of colonization barely lasted longer than three to five years.
Engineering activities were confined to two geographical regions. On the Gulf of Mexico, the work consisted of finding the best port and of improving the waterways. In the Louisiana interior, they had to build the necessary network of military outposts and commercial trading posts. This task led to the choice of the location of the colony's capital.

The engineers ran in problems with the interests of the Company, with those colonists who had already moved in, and with the poorly-distributed powers of the commander general and the ordonnateur. Still, they generally had enough authority to not fail at their task, and to impose their reasoned choices concerning the placement and shape of the town and the building techniques that should be used.

Letter from engineer Pauger complaining about houses built in New Orleans CAOM, C13A 6, f° 140-141, 19 août 1721

Moving the town of Mobile to a better location, abandoning Biloxi in favor of New Orleans, implanting forts and concessions near Indian villages, adopting regular town plans and simple architectural structures, and training specialized workmen on the spot-all of these actions, stubbornly defended by a mere handful of men, left a lasting mark on the countryside as well as on Louisiana's two cities.

The engineers who were the most influential in the development of Louisiana all died within a few years of each other (Le Blond de La Tour and Pinel de Boispinel in 1723, Pauger in 1726, and Devin in 1735), or returned hastily to France (Franquet de Chaville in 1724). Their successors, less susceptible to fever, carried out the lion's share of the work that they had planned-and in the less auspicious period of the decline of the Company of the Indies and the royal patronage.