When were Concrete masonry unit invented?

Concrete masonry units (CMUs), commonly known as concrete blocks, were invented in the late 19th century. The first patents for concrete block machines were filed in the 1830s, but they gained widespread popularity in the early 1900s, particularly after the introduction of reinforced concrete technology. Their use became more prevalent in construction during the 20th century, as they offered a durable and cost-effective building material.