The Twin Peaks Cemetery was filmed at the Sierra Madre Pioneer Cemetery in Sierra Madre, CA, about a ten minute drive from the Hayward house and General Store locations. A few fake graves were brought in and placed in the cemetery for the filming of Laura's funeral scene. Notably the large obelisk-shaped one seen above, behind Doctor Jacoby. Below: a few screen captures from the series followed by some of my photographs of the cemetery.
Below: the entrance to the cemetery and an aerial shot of the spot where Laura's grave was located.