I am not familiar with the book to which you refer. However, all the evidence i was able to find in a brief search suggests that all of those hung were hung on "Gallows Hill," in Salem, which later became notorious as "Witch Hill." To place that topographically, i suggest that you contact the office of the county engineers--in most jurisdictions, the county engineer's office is responsible for local maps. A local library in Salem may help, as well.
Giles Corey was "pressed" to death for refusing to plead (i.e., he would neither admit nor deny his "guilt"). Pressing meant that he was placed on the ground, and a large panel of stout wooden planks was placed over him, and stones were then piled on the panel until he was "crushed to death," although suffocation was the likely cause of death, when he could no longer draw breath into his lungs. At least four people died in prison, awaiting trial--some accounts list others, as many as a dozen others, as having died in prison; only four, however, are acknowledged as having died in prison in official records of the time.
Click here to be taken to a map. (On that page, select "Large Map" under the rubric "View the map."--you can enlarge that map by clicking on it after it has fully loaded. This is necessary to be able to read the detail of the map.)
This map was prepared in 1866 by a gentleman named Upham, and it shows the place of execution as an otherwise unnamed hill to the south of Salem village, and to the west of the town of Salem. In the lower right-hand corner of the map, near the bottom edge, you will see a hill marked with a "W" which is listed in the legend as the "place of execution." The hill is located south of "North River," which is fed by Goldthwait's or Gardner's brook and Proctor's Brook. The map is of "Salem Village," because a distinction is being made between the area of general settlement, with numerous farmsteads, and the town of Salem on a neck of land between North River and South River. The place of execution is west of the town of Salem on it's neck of land--once again, look in the lower right-hand corner.
