His work includes numerous commercial buildings, private homes, churches, schools and hospitals. Pfeiffenberger’s preference in architectural style are numerous including
Italianate,
Queen Anne,
Georgian Revival, and other designs are found throughout Alton in the form of magnificent mansions and other public buildings. Many of his structures like the
Western Military Academy, Lucy
Haskell Playhouse, the
McPike Mansion, and The Beall Mansion (originally the Job Drummond Mansion) located in the Middletown Historic District are listed on or are supporting structures in historic districts of the
National Register of Historic Places In 2015, the Lucy
Haskell Playhouse underwent a major exterior renovation. One hundred and thirty years after its construction, the playhouse began deteriorating. According to the Haskell Association "The house had lead paint on its exterior, which was in poor condition, and had to be removed before the playhouse was repainted. The playhouse also needed exterior carpentry work, including on the
soffit, fascia and porch floors before painting could begin." The association was successful in raising enough money to complete the renovations to restore the playhouse. Some of his buildings have been razed. Two of his designs, the McPike Mansion and the Captain Leyhe House, are reportedly haunted, and are featured stops on the Alton Hauntings and Alton’s Haunted Odyssey tours. Most recently on Wednesday, May 20, 2015 the Watson House, built in 1879, caught on fire. According to the
St. Louis Post-Dispatch, "The blaze completely consumed the kitchen floor, sending the refrigerator, dishwasher, microwave and cabinets tumbling into the basement." ==Civic service==