I think I read the same book you did, and the phrase you’re looking for struck me as it struck you, and has stuck with me:
The Case for Mars: The Plan to Settle the Red Planet and Why We Must, by Robert Zubrin, published by Simon and Schuster, 2012.
In it Zubrin describes the steps needed for human habitation on Mars, starting with the first and most critical step: manufacturing propellant for liftoff and return for the first visitors (because carrying enough fuel for the return trip from Earth is prohibitively expensive to lift out of Earth’s gravity well).
Here, he says:
In 1976, Professor Robert Ash, now of Old Dominion University, and some JPL collaborators published a paper laying out some simple, robust and well established (Gaslight era, to be precise) chemical engineering processes...
So I think what you’re looking for is:
Gaslight era
But I want to offer a caveat here: this is not a standard or generic term for any proven technology.
Instead, he’s saying for this specific purpose — manufacturing propellant in situ — the techniques developed and perfected during the 19th century by the first wave of “modern” scientists who discovered chemistry, would be sufficient for the purpose.
The goal of the book is to make a clear case that Mars can be settled in a practical and realistic way. Part of that is recognizing that some of the most critical processes don’t require “future tech”, or even high tech, and can be done on a [reasonable] budget.
In other words, the argument behind the phase in this context is:
The same fuel that those pioneers created processes to efficiently and effectively manufacture from simple ingredients, sufficient to move the world from candlelight to gaslight, to illuminate this world, in a sense, is also fuel sufficient to get our astronauts home from another world altogether.