Ridgway is shown meeting his victims in bars; in reality, most of them were sex workers or runaways last seen along Seattle's Pacific Highway South (Highway 99).
The film shows Ridgway working in a warehouse, but he actually spent more than 20 years as a truck painter (which proved crucial in establishing his guilt, as trace evidence showed microscopic spray paint spheres on his victim's clothing that were found to match with paint from Ridgway's workplace).
After killing his victims, Ridgway is seen leaving their bodies near a "Green River" sign; the real Ridgway disposed of the corpses by leaving them mainly in forested and overgrown areas around King County (including the titular river) where they weren't likely to be easily found, which helped him elude justice for so long.
In the end credits, the "fight choreography" credit is incorrectly spelled as "fight coreography".
During Gary's 1981 encounter with the prostitute named Hedy, he hands her a $100 bill. The bill he hands her has a contemporary design that was not introduced until 1996.
In one of the 1980s-era scenes, Gary walks past a sports bar with a neon "Fox Sports Net" sign in the window. Fox Sports Net did not exist until 1997.
1981 gas prices are over $2.00 per gallon.
During the first few seconds of the scene where Irene dresses up as a prostitute and enters Mona's bar, a very prominent camera shadow is visible on Irene's head as she enters the frame.
When Anna and Irene (Gary's wife) first meet, Anna addresses her by name despite having never met her nor even knowing who she was beforehand.