This study provides the first documentation of Serpukhovian (Upper Mississippian) calcareous algae from type Mississippian strata at the Southern Illinois Stone Company Quarry, located in Johnson County, Illinois, U.S.A. The red algal microflora within the lower part of the Kinkaid Limestone includes Vachardia multigena Brenckle et Sheng gen. et sp. nov. and Masloviporidium crassimuri Brenckle et Sheng sp. nov., as well as a diverse assemblage of stacheiins. The algae were found in fossiliferous packstone/grainstone and ooid/coated-grain grainstone deposits. The morphological features of Vachardia are close to those of Masloviporidium, but further research is required to confirm evolutionary relationships. Additionally, the stacheiins include various morphologies that do not align closely with established species, highlighting the complexity and diversity of the algal community.