These images show the metal lath that supports the plaster in the courtroom. Our conversation quickly turned to pondering when this metal lath might date to, and how extensively was the courtroom remodeled in the 1930 work overseen by James Spain? We ruminated between the thoughts that the metal lath implied the 1930 work actually gutted the courtroom completed to the studs, and the possibility that the metal lath actually date to the 1891 construction.
While the first metal laths were patented in 1797, modern metal lath dates to the late 19th century. Its creation arose from the need to fireproof buildings by eliminating wood components, in this case it was replacing wood lath with metal. Metal lath use really took off in the late 1870s when iron and later steel production was capable of producing thin but strong metal sheets at a reasonable cost. Most lath in the 1880s & 1890s was perforated which the Washington County Courthouse metal lath definitely is. In 1894 the magazine the American Architect and Building News discussed the two kinds of commercially available metal lath. One was a 16 gauge wire mesh-a type precursor to modern expanded metal lath- and the other was “26 gauge metal crimped-up… or corrugated (Cincinnati Corrugating Company’s), with a series of perforations to make a clinch for the plaster”.
In their 1888 catalogue the Cincinnati Corrugating Company stated “We have patrons in every state and territory, and from Canada to Mexico inclusive.” Assuming this was not hyperbole, that would mean their products were in use in Mississippi. They also stated that at that time their metal lath was being used extensively in government buildings, which it might not be a big surprise that the Washington County Courthouse is one of those. While the Cincinnati Corrugating Company did not have a monopoly on perforated metal lath manufacturing, they were seen as innovators due to using corrugated iron stock. The corrigation had two benefits; acting as furring and to impart additional stiffness to the lath. The corrugation acting as furring gave space between the lath and the studs along with allowing for “ample rest for the plaster”. The strength from corrugation allowed for thinner , less weighty iron sheet stock to be used. 
Metal laths would soon be exalted not only for their fire preventive-ness but also for the ease & speed of installation and low-cost vs. wood lath. Expanded metal lath was well-known to architects by 1896, and its installation was such a major industry by 1899 it necessatated the establishment of the Wood, Wire and Metal Lathers’ International Union. By the 1910’s expanded metal lath was the industry norm as seen in the plethora of manufactures examples in the 1914 Metal Lath Hand-Book.
So to conclude with the answer to our Washing County Courthouse metal lath question; what it looks like happened in the courthouse is that the perforated corrugated metal lath was the original and there was a cove to the ceiling in 1891. The 1891 ceiling and cove were ditched in 1930, but the 1891 flat wall plaster was kept in place.
While perforated lath would continue to be used later on in the 20th century, it was only when a very rigid back was needed say as a backing for tile. Though old method and materials always hang on (and without seeing the building in person) I would wager to say that the lath we see would date closer to 1891 than 1930. Since we all cannot go see this attic space in person its great we have the MDAH HRI database sharing these images with the world. Did this lath-ing matter test your metal?
1 McDonald, Marylee. United States. National Park Service. Preservation Brief 21: Repairing Historic Flat Plaster Walls and Ceilings.. Washington DC: , 1989. Print.
2 Hill, George. “Slow Burning Construction.” American Architect and Building News. 21 04 1894: 28. Print.
3 “Iron Lath.” Catalogue of the Cincinnati Corrugating Company. Nov 1888: 19. Print.
4 Kidder, Frank Eugene. Building Construction and Superintendence, Vol. 1. 1896. Print.
5 McMaster, H.B. Associated Metal Lath Manufactures. Metal Lath Hand-Book Youngstown Ohio:, December 1914. Print.
6 Concrete Steel Company of New York. Havemeyer bars & building products. New York:, 1925. 30. Print.