There is an excellent article in the September 14th issue of the New Yorker, detailing Robert Frank’s journey across the States and a review of the book Looking In: Robert Frank’s “The Americans.”
Anthony Lane writes in the article:
It had been a year, more or less, since he embarked, and there was much to reflect upon. Luckily, he’d taken a few photographs along the way.
In fact, he took around twenty-seven thousand. There were more than seven hundred and sixty rolls of film to develop: an impressive tally, even to snap-happy profligates of the digital age. Then there were contact sheets to print and mark up; from those, he made a thousand work prints, which were tacked to the walls of his apartment on Third Avenue, near Tenth Street, or laid flat on the floor for closer inspection, before being whittled down to a hundred. The final count, from all those months on the road, was eighty-three pictures: enough for a slim book, which was published in November, 1958, in Paris, as “Les Américains,” and here, in January, 1960, as “The Americans.” For his pains, Frank was paid two hundred dollars in advance, a sum that rose to just over eight hundred and seventeen dollars by the end of the year. By then, the book was out of print.
The original book from 1959:

Robert Frank ‘The Americans’ New York: Grove Press 1959
Additional contact sheets from the hardcover edition of “Looking In”:

proof sheets from Looking In: Robert Frank's " The Americans "