Factual error: None of the Swedish wedding traditions Ingrid mention actually existed in the 19th century and the bread she's baked is not traditionally Swedish. When she later speaks in her mother tongue it's definitely not Swedish.
Dr. Quinn, Medicine Woman - S1-E1
Factual error: When the woman is giving birth and Dr. Quinn has to perform a c-section, she gives the baby to Mrs. Cooper, and after about a minute, she gives the baby to the mother. Dr. Quinn then leans towards Mrs. Cooper and they smile happily; she doesn't attempt to continue the "surgery". Even nowadays doctors need several minutes to close up again after a c-section, so there is no way that Dr. Quinn was anywhere near finished. Leaving the patient cut open on the bed is pretty irresponsible, something she would never do as she has to prove that she is a good M.D. (00:30:00)
Factual error: Marjorie's tragic death: The Quinn family has her funeral in the town cemetery, where she did not belong, instead honoring her death with a vigil, then transporting her body back to Boston, to be buried properly with her Quinn relatives: A common respect reserved for dignitaries; which technically the Quinn family was/is, and soldiers.
Factual error: Grace sings "Precious Lord Take My Hand." The song wasn't written until the 1930s.
Where the Heart Is (1) - S2-E6
Factual error: During the arrival at Beacon Hill, Colleen tells the girls during tea that the streets in Colorado Springs are all dirt, not the cobblestones as corrected by one of the girls (when Colleen referred to the Boston streets as rocks). When, in fact, several road scenes around Boston in several scenes are dirt or dried mud.
Factual error: Horace catches the ball during the first half of the final competition as Otis approaches 4th base/pitcher's mound, which outs him automatically yet Michaela nor the team call it.
Suggested correction: He was out. It was obvious that he was out when Quinn said he caught it. There would be no point in having to call him out. Otis is then seen telling his players to return to their bases because they could be tagged out. But he doesn't bother going anywhere because even he knew he was out. And we do see the players get called out.
Factual error: Near the end, when Horace is delivering Lincoln's Declaration speech, Mike and Sully are talking, you can see their breath. Indicating this was shot during the winter, when it's supposed to be July 4th Independence Day.
Factual error: In the later seasons (4-6) all the characters keep referring to their location as 'Colorado Springs' instead of just stating 'here'. Example: "I told him to stay in Colorado Springs" instead of just stating "I told him to stay HERE"