RAPID CITY, S.D. - A Rapid City man was sentenced to 25 years in federal prison for leading a large-scale methamphetamine trafficking operation connected to a Mexican drug cartel.

Guillermo Calderon, also known as “Memo,” 38, was sentenced this week for Conspiracy to Distribute a Controlled Substance. During sentencing, the judge emphasized that the meth Calderon trafficked was 100% pure and from a Mexican cartel.

Investigators say Calderon was the ringleader of a conspiracy that funneled significant quantities of meth into both the Pine Ridge Reservation and Rapid City. Calderon used guns and threats of violence throughout his drug distribution scheme.

In Jan. 2024, Iowa law enforcement arrested Calderon while he was transporting roughly 20 pounds of methamphetamine into South Dakota.

U.S. District Judge Karen Schreier called Calderon the most violent and culpable member of the network, denouncing the lasting harm his actions inflicted on South Dakota communities.

“Calderon led a dangerous operation that funneled large amounts of methamphetamine into Pine Ridge and Rapid City, bringing violence and addiction into vulnerable communities,” said Special Agent in Charge Alvin M. Winston Sr. of FBI Minneapolis. “Today’s sentencing reaffirms that those who bring cartel-linked drugs into our communities will be brought to justice. 

A federal grand jury indicted Calderon in Feb. 2024, and he pleaded guilty on March 26, 2025.

“Methamphetamine is ravaging communities throughout South Dakota, leaving a trail of heartbreaking addiction in its path,” said U.S. Attorney Alison J. Ramsdell. “Calderon played a significant role in perpetuating this problem by trafficking methamphetamine into Rapid City and within the Pine Ridge Reservation. Thanks to our skilled federal and tribal law enforcement partners, Calderon will now spend serious time in federal prison.”