A costume ball, a parade, musical performances and a visit by twin TV stars Lindsay and Sidney Greenbush are among the activities planned for Holy Terror Days in Keystone on Friday and Saturday.

The visit by the Greenbush twins is sponsored by the Keystone Area Historical Society and the Keystone Chamber of Commerce. The twins will be available for autographs and pictures and will also be participating in the numerous events that are being planned for Holy Terror Days.

Lindsay and Sidney Greenbush, the identical twins who appeared on television's "Little House on the Prairie" series from 1974-1982, playing the role of Carrie Ingalls, will make an appearance from 7 p.m. to 10 p.m. Friday at the Old Fashioned Family Costume Ball at the Keystone Community Center. They also will appear in the 11 a.m. parade Saturday and at the free Living History School from noon to 2 p.m. Saturday at the Keystone Historical Museum.

"Little House on the Prairie" was based on the books of Laura Ingalls Wilder. Carrie Ingalls, the younger sister of Laura Ingalls Wilder, came to Keystone in 1911 to be a reporter for "The Recorder," a Keystone newspaper. Carrie married David Swanzey, a local widower and mining man. She lived in Keystone until her death in 1946.

Today, Lindsay Greenbush is an amateur boxer and is studying for her personal trainer certification. She is actively involved with Kid Gloves Boxing Studios in Simi Valley, Calif., which, in addition to focusing on physical fitness, also aims keep kids away from negative influences including gangs and drugs.

Sidney Greenbush remains active in equine competitions and also has a line of original designer jewelry that is available to her fans through their official fan Web site www.greenbushtwins.com.

The Hill City Slickers will appear Friday at the Old Fashioned Family Costume Ball.

On Saturday at 4:30 p.m., Deadwood Songbook will perform a free concert of popular music of the Black Hills Gold Rush Days at the Keystone Community Center. Deadwood Songbook is the result of research by Hank Harris in cooperation with the Adams Museum in Deadwood. Harris extensively researched music from Deadwood's gold camp days, capturing the music of the era.

Deadwood Songbook band members include Hank Harris, who has been playing, writing and recording music in South Dakota for decades; Kenny Putnam, two-time South Dakota fiddle champion who has appeared at The Grand Ole Opry and on "The Tonight Show" in addition to performing nationally and internationally; and Ricky Jacobsen, who has performed in the Black Hills for more than 30 years.

For more information or to make a donation, call Bob Hanson 666-4481 or Sandi McLain 666-4847.

Here is the schedule:

Friday, Sept. 5

7 p.m. - 10 p.m. - Old Fashioned Family Costume Ball, community center; entertainment by the Hill City Slickers; prizes for best costumes; food will be available. The Greenbush twins will sign autographs.

Saturday, Sept. 6

All day - Softball tournament & Mule Skinner Biscuits, community center

9:30 a.m. - 10:30 a.m. - Horse poker ride, horse judging and live entertainment with Paul Larson, Big Thunder Gold Mine

10 a.m. - Old Tyme Crafts and Vendors, Big Thunder Gold Mine

10:30 a.m. - Parade line-up, Keystone Mall

11 a.m. - Holy Terror Parade

11:45 a.m. - Chuck-wagon style lunch and live entertainment with Wildcat and Dutch, Big Thunder Gold Mine

Noon - Free Living History School, Greenbush twins and Rick Mills autographing, Keystone Historical Museum

1 p.m. - History enactment, Big Thunder Gold Mine

2 p.m. - Live entertainment with Paul Larson and children activities, community center

2:30 p.m. - Holy Terror Day auction, community center

4:30 p.m. - Community barbecue and live entertainment with Deadwood Songbook, community center