The sanctuary at Immaculate Conception has gone through several alterations since the church was dedicated in 1904. Originally, there was a large marble altar at the rear of the apse in the sanctuary. It was an ornate marble piece in a gothic style. It not only functioned as the altar, but served as a focal point of the entire church. In 1964, the altar was moved out into the sanctuary which allowed the priest to face the congregation when celebrating mass. The new altar was covered by a contemporary baldacino that rested on four slender columns. It served to enhance the presence and significance of the altar. As part of the renovation, a contemporary decorative wall was installed behind the altar that served as a backdrop and housed the tabernacle.
During the 2006 renovation to the church, there were several alterations to the sanctuary. The baldacino was removed and the contemporary decorative wall behind the altar was replaced with a wood reredos. A reredos is a decorative screen or ornate wall treatment located behind the main altar of the church. The word reredos is derived from the French terms "Arere" meaning "behind" and "dos" meaning "back".
Historically, the reredos is one of the most ornate, highly decorated elements within the church. Its detail and craftsmanship create a sense of visual focus to the church interior and emphasize the importance of the sanctuary and altar. The new reredos is crafted of solid American cherry hardwood. The gothic inspired pinnacles and abstract crockets are reflective of traditional gothic architecture and draw from the fleche or metal spire on the roof of the church.
The reredos was constructed by the E.C. Snyder Company of Harrisburg, Pa. It is over twenty feet tall and thirty feet wide. The original tabernacle was incorporated into the new reredos and sits on a piece of polished green marble. Contained within the marble is the relic from the original high altar. On the face of the marble is a small gilt cross carved into the stone to signify the location of the relic.