Final answer:
The Wainwright Building by Louis Sullivan is distinguished from International Style buildings through its use of ornamentation, whereas International Style emphasizes volume, minimalism, and functionalism without ornament.
Step-by-step explanation:
The feature that distinguishes Louis Sullivan's Wainwright Building from International Style buildings is the use of ornamentation. Sullivan's Wainwright Building, a hallmark of the Chicago School of architecture, employed steel-frame construction with masonry cladding and had characteristics such as the 'Chicago window'. This style did use some exterior ornamentation, in contrast to the International Style which emphasized the rejection of all ornament and color, focusing on minimalism and functionalism.
The International Style, which developed later, was hallmarked by an emphasis on volume over mass – featuring industrial materials, modular forms, and a notable absence of ornamentation, with flat surfaces alternating with glass. Sullivan's approach was more transitional, linking the solidity and familiarity of 19th-century masonry with the burgeoning modernism of steel-frame construction.