This study expands upon a previous analysis of the Clarence H. Webb collection, which resulted in the identification of two discrete shapes used in the manufacture of the base and body of Smithport Plain bottles. The sample includes the Smithport Plain bottles from the Webb collection, and four new bottles: two previously repatriated specimens in the Pohler Collection, and two from the Mitchell site (41BW4) to test whether those specimens align morphologically with the Belcher Mound or Smithport Landing specimens. Results indicate significant allometry and a significant difference in Smithport Plain body and base shapes for bottles produced at the Smithport Landing and Belcher Mound sites in northwest Louisiana. The Pohler and Mitchell specimens do not differ significantly from those found at Smithport Landing or Belcher Mound. Analysis of the aggregated sample indicates some significant relationships between bottle shape and size, bottle shape and type, and bottle shape and site, highlighting assemblage-level and type-specific variability. The test of morphological disparity by period indicates a possible gradual trend toward standardization, and the test of morphological integration indicates that Caddo bottles are significantly integrated, meaning that those discrete traits used to characterize their shape (rim, neck, body, and base) vary in a coordinated manner. The iterative development of this research design can lead to substantive theoretical gains that augment discussions of decorative components and motifs as well as ceramic technological attributes.