Damon Hininger, the chief executive of CoreCivic, which operates private prisons and immigrant detention centers, opened an investor call last month on a buoyant note.

“I’ve worked at CoreCivic for 32 years, and this is truly one of the most exciting periods in my career,” he said, adding that the company was anticipating in the next several years “perhaps the most significant growth in our company’s history.”

CoreCivic, GEO Group and some smaller private prison companies are becoming a key cog in the Trump administration’s plan to hold and then deport vast numbers of undocumented immigrants. Already in the past week, CoreCivic and GEO have announced new contracts and executives say they are expecting more.

Predictions for such a stratospheric trajectory in revenue for these companies did not look to be in the cards just four years ago.

Public sentiment had turned against its industry, amid accusations of safety and health violations and the stigma of profiting from the incarceration of immigrants. Big banks, responding to pressure campaigns from activists, had announced they were going to stop issuing new loans to the companies. The newly elected president, Joseph R. Biden Jr., had vowed on the campaign trail to end contracts with the companies.