  pine grove township is a township in warren county, pennsylvania, in the united states. as of the 2000 census, the township population was 2,712. ==history== the guy c. irvine house was added to the national register of historic places in 1978. ==geography== according to the united states census bureau, the township has a total area of 40.0&nbsp;square miles (103.5&nbsp;kmÂ²), of which, 39.7&nbsp;square miles (102.8&nbsp;kmÂ²) of it is land and 0.3&nbsp;square miles (0.7&nbsp;kmÂ²) of it (0.68%) is water. ==demographics== as of the census of 2000, there were 2,712 people, 1,084 households, and 822 families residing in the township. the population density was 68.4 people per square mile (26.4/kmÂ²). there were 1,193 housing units at an average density of 30.1/sq&nbsp;mi (11.6/kmÂ²). the racial makeup of the township was 98.60% [[wh
Townships_in_Pennsylvania Townships_in_Warren_County,_Pennsylvania