The BA&P was an electrification pioneer, converting in 1913 and being the first primarily freight railroad to electrify. Electrification was at 2,400 volts DC; the work was performed by General Electric and the railroad's own staff. As described in a period article: "The length of this line was 30 miles, having a total of 114 miles of single trackage, and considerable heavy grade. The electric locomotives hauled heavy ore trains and the operating results from every viewpoint far exceeded expectations. Mr. John D. Ryan, principal owner of this road,[...] (says) that "the cost was within the original estimate, the operation has been an unqualified success and the economy at least 50% in excess of the promises of the engineers at the time the work was undertaken. The tonnage handled over the lines increased over 50% in three years ; no difficulty has been found in moving the increase, and in the opinion of the railway managers the main line and two of the principal branches had reached the capacity of single track when electrification came into use." "
The railroad as a whole lost much of its business following the closure of the Anaconda smelters, and in 1985 was sold to a consortium of local investors and reconstituted as the Rarus Railway (reporting markRARW). On July 19, 2007, Patriot Rail Corporation, the parent company which acquired Rarus Railway in May 2007, announced that the railway's name was officially changed back to Butte, Anaconda and Pacific Railway.