Twenty-one people, most of them from Franklin County, have pleaded guilty in the past month to federal charges in a methamphetamine conspiracy ring.

The network manufactured and distributed methamphetamine from 2009 through 2011.

The defendants who pleaded guilty recently are among more than 50 people who were charged in the extensive investigation that was spearheaded by the Franklin County Narcotics Enforcement Unit.

Other agencies that took part in the investigation were the federal Drug Enforcement Administration and the Kirkwood and Pacific police departments.

Ann L. Matchell, 47, Labadie, pleaded guilty last Friday and Shelly M. Peterman, 42, Villa Ridge, entered a guilty plea last Thursday, according to the U.S. attorney’s office.

The following co-defendants entered pleas in August, September and earlier in October:

Jerry A. Hendrickson, 27, Franklin County; Jerry M. Walling, 48, Catawissa; Jason S. Sparks, 32, Villa Ridge; Dale M. Harris, 44, Pacific; Ethan M. Lepinski, 47, Pacific, Mo.;

William L. McKinney, 21, Pacific; Elaine M. Scroggs, 23, Pacific; Miranda J. Everhart, 21, Pacific; Aaron A. Lyerla, 33, Arnold; Larry R. Collier, 40, St. Clair;

Tammy L. Busch, 41, Pacific; Andrea R. Dowling, 28, Villa Ridge; Michael S. Pich, 32, Villa Ridge; Michelle A. Sizemore, 37, Fenton;

Douglas E. Hughes, 29, Pacific; Amy N. Bueker, 25, Pacific; Sarah A. Matchell, 23, Labadie; Eric E. Lyerla, 37, Pacific; and Angela J. Holley, 33, Arnold.

Each defendant appeared before U.S. District Judge Stephen N. Limbaugh Jr.

They are scheduled for sentencing in December 2012 and January 2013.