She was also found guilty of tampering with physical evidence.
"Of all the many emotions of the magical first moments of a baby's life, of all the many tender moments a mother shared in that first embrace with a completely helpless and fragile life, smothering a newborn and pitching its body over a fence in the cold of January is impossible to understand," District Attorney George Brauchler said.
"Who are we as a people that someone among us has such disregard for the most innocent of lives - a life they helped create? Disgusting."
The baby reportedly lay in the neighbour's backyard for 16 hours as the mother went about her day.
"This defendant went about her day, knowing her unnamed daughter was there, helpless. She thought and made that choice," Deputy District Attorney Valerie Brewster told the jury.
"That little girl was on that deck for 948 minutes," she added.
"This defendant hurled her newborn 11 feet (3.3m) over an 8-foot (2.4m) fence, knowingly consigning her to her death. This little girl died in the cold without the dignity of even a name," Chief Deputy District Attorney Christopher Gallo said in court.
The mother will be sentenced on November 15. The mandatory sentence is life in prison without the possibility of parole.
The state of Colorado has a Safe Haven Law which allows a parent to hand over a newborn, up to 72 hours old, to any fire station and hospital, no questions asked.