Castor's Ridge begins as a camp around a fledgling farmhouse. The first time coming across, should be shortly after leaving Horseshoe Overlook for the first time and exploring the surrounding area around the small frontier town of Valentine. Arthur Morgan encounters them as a father is watching his two sons put up a wall on the front of the house. They drop the wall and the father berates them, telling them to put it back up, then telling them to back away before they make it worse. The sons go to a campfire and lament their father's nagging.
The second encounter occurs when Arthur sees the camp under attack by a group of four extortionists. Once the gunmen are fended off, the father thanks Arthur for his help, stating they were attacked when he refused to pay protection money. He then returns to the house, demanding to know why his sons didn't shoot at them. The sons respond that they didn't have any guns.
The third and fourth encounter both involve money or supplies. On the third encounter, Arthur finds the house mostly built, and the father says they are nearly done, but need more supplies or they'll have to leave. Arthur can give them $100 or agree to get supplies for them. In order to get supplies, Arthur must go to the Appleseed Timber Company camp in Big Valley, and order supplies from them. The wagon of timber costs $75, and can be delivered to Castor's Ridge. Alternatively a wagon can be stolen from the Appleseed Timber Company, from Valentine or from an NPC on the road driving one.
Arthur can return to the location for one last encounter with the father. If Arthur agreed to give him money, the father will pay Arthur the money he's owed. He says he has sold the house to a farmer who's moving south.
Years later in 1907, John Marston can encounter the farmhouse. It now has a small garden with vegetables in the front, enclosed by a fence. John can encounter the farmer and his wife. If the house is entered, they will ask John to leave.