13-month-old Silas Ojeda was reported missing after his grandfather learned from the mother that she had not seen the boy since October 22.
Logan Rogers was arrested October 28 in connection with the death of the boy.
Rogers, the boyfriend of Ojeda’s mother, told Judge Thomas Campbell that the boy died after falling off of a counter.
Rogers pleaded guilty during his arraignment in Cheyenne. He faces up to 20 years in prison.
Prosecutors dropped a charge of endangering the boy after exposing him to methamphetamine.
Police said Rogers admitted to disposing the boy’s body.
Officials believe the body was dumped in a trash bin at Laramie County Community College in Cheyenne.
Crews began searching the landfill near Ault after authorities believed the contents of that trash bin were taken to the landfill.
Authorities began their search of the landfill on November 1 and found no evidence of the missing boy.
The Laramie County Sheriff’s Department in Wyoming said more than 3.3 million pounds of refuse were searched by more than 400 people.
The search for the body ended Monday after authorities came up empty in their search.
Authorities arrested the child’s mother, Rhianna Ojeda, last Thursday. She refused to speak with detectives and was released last weekend.
The Laramie County Sheriff’s Department in Wyoming said the case remains under investigation.