Simpson Lake, in Simpson Park, 1234 Marshall Rd, Valley Park, MO 63088. Go further than the main entrance to the park, then turn left at the MSD Treatment Plant, which is 1000 Grand Glaize Parkway, Valley Park, Missouri 63088 (turn before the overpass). Go north a short distance toward then MSD entrance, then "our" parking lot on the right at these coordinates:
N 38.55787 ; W090.47247

Location