The population of New Orleans increased dramatically in the years following Louisiana statehood. With the explosive unregulated growth came all of its concomitant problems. In the early years, a small population meant only a few butchers working in the region. By 1868, an estimate reported more than 150 slaughterhouses in the New Orleans area. In 1869, there were 40 slaughterhouses in just the Fourth District (the former City of Lafayette). Hundreds of thousands of animals were slaughtered every year. There were no public sewers. Those slaughterhouses resulted in a daily deluge of waste material, blood, and offal that was improperly dumped into both the street and the river.
For colorful reports of the environment, please see The State of Louisiana, ex rel. S. Belden v. Wm. Fagan, et al., 22 La. Ann. 545 (1870).
Why did the Louisiana Legislature get involved in a local dispute about butchers? At that time, New Orleans was the largest city in Louisiana, and one of the largest cities in the country. However, back then the western edge of New Orleans was Felicity Street. Also, the city of New Orleans, located within Orleans Parish, had no power to regulate the municipalities or parishes up river. The City of Lafayette was incorporated in 1846. When it was merged into New Orleans in 1852, the land still remained part of Jefferson Parish. In 1850 Jefferson City was incorporated, and lay within Jefferson Parish as well. The legislature merged Jefferson City into both New Orleans and Orleans Parish in 1870, one year after the Slaughterhouse Act had been passed. Therefore, the Louisiana Legislature's Slaughterhouse Act was aimed at a large metropolitan region, not just a single city.
1846 Act No. 40 Incorporation of Lafayette in Jefferson Parish.
1850 Act No. 93 Incorporation of the City of Jefferson in Jefferson Parish
1852 Act No. 72 Lafayette merged into New Orleans, but still remains part of Jefferson Parish.
1870 Act No. 7 Merged Jefferson City into New Orleans, and extended Orleans Parish boundary.
Union forces occupied New Orleans after it fell in April 1862. When General Butler entered the city, he was shocked by the stench and filthy condition of New Orleans. Under marshal law, he oversaw the clean-up of the city, something that had been politically impossible before, when city officials had refused to take action.
General Butler's cleanliness campaign and enforced sanitary conditions allowed a dramatic drop in yellow fever cases reported in New Orleans. In 1858, a yellow fever outbreak had claimed 4,845 lives. During the occupation, despite a population of more than 170,000, there were only a handful of deaths from yellow fever. Once the occupation ended, and city officials were back in control, sanitation standards lapsed, and the death toll shot back up. In 1866, 185 people died; in 1867, 3,107 people died from yellow fever.
See History of Yellow Fever by George Augustin, 1909. The New Orleans yellow fever deaths during the war may be found at https://archive.org/stream/historyofyellowf00auguuoft#page/870/search/1862