Enter Conservation in the United States. Charles Richard Van Hise (who was an advisor on conservation to President Theodore Roosevelt) wrote the following in his book "The conservation of natural resources in the United States": (page 379)
Conservation means "the greatest good to the greatest number - and that for the longest time".
Pretty straight forward. Utilitarianism is often thought to start with Jeremy Bentham(in a classical/modern sense), and here is what he says in his book "A Fragment on Government": (In the preface, page ii)
it is the greatest happiness of the greatest number that is the measure of right and wrong
That's Bentham's fundamental axiom,(Mill also used the phrase in his own way) to which you will see far and wide a seemingly limitless variation of this quote, as an explanation of what Utilitarianism actually is.
It's virtually identical. And Hise wasn't alone. Gifford Pinchot, a Bull Moose/Progressive republican and first chief of the US Forest Service, wrote this in his autobiography "Breaking New Ground": (page 353)
"Conservation is the greatest good of the greatest number for the longest time"
Despite the fact that this is almost verbatim what Hise wrote, on page 326 Pinchot writes that McGee was who convinced him of this view. The book says W J McGee, which is William John McGee, who on page 359 Pinchot considered to be "the scientific brains of the Conservation movement all through its early critical stages".
I highlight this for one specific reason: in a lot of ways, American progressivism and British Fabianism grew and evolved in similar ways, along similar ideological lines. Henry George was a American, yet his writing was significant in the development of the Fabian Society. And here's clear utilitarian thought(whether imported or domestically developed, probably doesn't matter) right there as well.