They also found two human-built pits dug 15,000 years ago to trap mammoth, believed to have been the first find of mammoth traps set by humans.
Researchers from Mexico's National Institute of Anthropology and History said on Wednesday (local time) the pits were found during excavations on land that was to be used as a garbage dump.
The pits were about 1.7 metres deep and 25 metres in diameter.
The institute said hunters may have chased mammoths into the traps. Remains of two other species that disappeared in the Americas — a horse and a camel — were also found.
"This is the largest find of its kind ever made," the institute said in a statement.
The skeletal remains were found in Tultepec, near the site where President Andres Manuel Lopez Obrador's Government is building a new airport for Mexico City.
Some of the remains bore signs that the animals had been hunted, leading experts to conclude that they had found "the world's first mammoth trap", the statement said.
Mammoths lived here for thousands of years. The herds grew, reproduced, died, were hunted …they lived alongside other species, including horses and camels," archaeologist Luis Cordoba told journalists.
Researchers said at least five mammoth herds lived in the area of the find. Mexico has been the scene of surprising mammoth discoveries before.
In the 1970s, workers building the Mexico City subway found a mammoth skeleton while digging on the capital's north side. It was unclear if plans for the garbage dump would proceed.