What invention did Mark Twain invest heavily in that contributed to his bankruptcy?

The invention Mark Twain invested heavily in that contributed to his bankruptcy was the Paige Compositor. Developed by James W. Paige, it was a mechanical typesetter intended to replace human workers who arranged individual pieces of movable type.

Twain, a former printer, became fascinated by the machine and began investing in it around 1880. He eventually spent roughly $200,000 to $300,000, including much of his book income and part of his wife Olivia's inheritance. Although the machine could work impressively in demonstrations, it was extremely complex, unreliable, and difficult to adjust.

The Paige Compositor never achieved profitable commercial production. Its failure coincided with losses at Twain's publishing company, Charles L. Webster and Company, and the financial strain eventually led him to declare bankruptcy in 1894. The more practical Linotype became the successful rival in mechanical typesetting.

A common mix-up is calling the invention simply a “typesetting machine.” That description is technically accurate, but Paige Compositor is the specific name of the invention associated with Twain's disastrous investment.