In 1955, Triangle Publications bought the channel 15 license from Lebanon Television but the sale was held up by challenges from nearby Harrisburg television stations WHP-TV, WCMB-TV (now defunct) and WTPA-TV (now WHTM-TV) and Reading television station WHUM-TV (also now defunct) and the station finally returned to the air with increased power on May 2, 1957. Under Triangle ownership, the station became a part-time ABC affiliate and received other programs from then sister station WFIL-TV (now ABC owned-and-operated station WPVI-TV) in Philadelphia. Triangle changed the station's call letters on New Year's Day 1959 to WLYH-TV (representing its service area of Lebanon, York and Harrisburg). In 1963, it became a CBS affiliate as part of the Keystone Network, a three-station network serving South Central Pennsylvania that also included WHP-TV (channel 21) in Harrisburg, and WSBA-TV (channel 43, now WPMT-TV) in York. This arrangement was necessary in the days before cable television gained much penetration. South Central Pennsylvania is very mountainous, and UHF stations have never covered rugged areas very well. It created a strong combined signal with 55 percent overlap, and was a major factor in the decision to collapse South Central Pennsylvania into one giant market two years later.