Final answer:
The most important development in manufacturing during the early 19th century was the interchangeable parts concept, which allowed for faster and more efficient production. every other like part, each machine as a whole an exact duplicate of every other machine of the same type and manufacture.
Step-by-step explanation:
The most important development in manufacturing during the early 19th century was interchangeable parts concept. Eli Whitney, known for inventing the cotton gin, also developed the idea of interchangeable parts. This concept allowed for the easy replacement of broken parts with identical ones, making production faster and more efficient.
By standardizing parts, machines and products could be produced more quickly, each part being an exact duplicate of every other like part, each machine as a whole an exact duplicate of every other machine of the same type and manufacture.