The Operative Plasterers' & Cement Masons' International Association (OPCMIA) is a trade union representing skilled workers in the construction industry, specifically those who work with plaster, cement, and concrete. Founded in 1864, it is one of the oldest building trades unions in North America. OPCMIA members specialize in applying and finishing various types of plaster and cement-based materials. Plasterers work on interior and exterior walls, ceilings, and decorative elements, creating smooth or textured surfaces and ornamental designs. They apply plaster over lath, foam, or other substrates to form walls, ceilings, and architectural features. Cement masons focus on working with concrete in various forms. They pour, spread, smooth, and finish concrete for structures like foundations, floors, sidewalks, and roads. Their work involves setting the forms that hold concrete, ensuring proper curing, and creating specific textures or patterns on concrete surfaces. The union provides extensive training programs to ensure its members stay current with evolving techniques and materials in their craft. OPCMIA advocates for fair wages, safe working conditions, and benefits for its members, playing a crucial role in maintaining high standards in plastering and concrete work across the construction industry.