SIMI VALLEY, Calif. — In the vast, cool basement of the Ronald Reagan Presidential Library here, Jennifer Mandel held up a hand-drawn map of the United States from the late 1970s.

A Reagan campaign staff member had colored states with red and blue ink at the start of his first successful run for president.

The map is one of 750,000 pages from that campaign released to the public last week after two years of painstaking work by Ms. Mandel and several other archivists. The collection includes strategy memorandums, handwritten speeches, and more than 100 polling books that divide respondents into subtly different categories, including “quite likely” and “very likely” to vote.

“If someone is a political junkie, this is a Candyland for sure,” Ms. Mandel said, straining to reach one of the 920 boxes she and the others had sorted and cataloged. “You get a real sense of how he used to work.”