In the original portion of my 1949 Colorado home, there are several GFCI outlets in the family room and bedroom. It looks like at least one room's outlets are not grounded, would this be why someone installed them? Not every outlet has been updated in that room though. I am in the process of updating the outlet and was basically wondering if I should keep the GFCI or could replace them with non-GFCI?
Following is an excerpt from the National Electrical Code:
406.4(D)(2) Non–Grounding-Type Receptacles. Where attachment to an equipment grounding conductor does not exist in the receptacle enclosure, the installation shall comply with (D)(2)(a), (D)(2)(b), or (D)(2)(c).
(a) A non–grounding-type receptacle(s) shall be permitted to be replaced with another non–grounding-type receptacle(s).
(b) A non–grounding-type receptacle(s) shall be permitted to be replaced with a ground-fault circuit interrupter-type of receptacle(s). These receptacles shall be marked “No Equipment Ground.” An equipment grounding con-ductor shall not be connected from the ground-fault circuit-interrupter-type receptacle to any outlet supplied from the ground-fault circuit-interrupter receptacle.
(c) A non–grounding-type receptacle(s) shall be permitted to be replaced with a grounding-type receptacle(s) where supplied through a ground-fault circuit interrupter. Grounding-type receptacles supplied through the ground-fault circuit interrupter shall be marked “GFCI Protected” and “No Equipment Ground.” An equipment grounding conductor shall not be connected between the grounding-type receptacles.
Also, since 2011 all dwelling unit receptacles are required to be tamper-resistant and replacements are required to adhere to this.
You also need to check local codes to see if your replacement receptacles are required to be Arc Fault Circuit Interrupter type. The NEC now requires them in most of the house but some states and municipalities have opted out of this requirement.
Installing a non-grounded GFCI -- and properly labeling it as such -- is the correct solution to allow plugging in grounded appliances where no ground is available.
As to why they did this at those specific locations, you'd have to ask the prior owner. Maybe that's where the fish tank was.