Several new Sphagnum species occurrences are reported for each of Butler, Crawford, Mercer, and Venango Counties in northwestern Pennsylvania. Five new county records are reported from Butler County: S. centrale, S. cuspidatum, S. flexuosum, S. girgensohnii, and S. subtile. Sphagnum contortum and S. palustre are new to Crawford and Mercer Counties, respectively. Seven new county records are reported to Venango County, namely, S. cuspidatum, S. girgenshonii, S. magellanicum, S. majus, S. palustre, S. subsecundum, and S. warnstorfii. Additionally, we report the continued occurrences of S. girgensohnii from Allegheny County and S. capillifolium from Butler County that were previously known only from historical records of collections made 70 and 80 years ago, respectively.