Patricia C. Wrede's Frontier Magic series is set in the past in a sort of alternate United States with magic. The first book in the series is Thirteenth Child. The main character is a twin. Her brother is the seventh son of a seventh son and therefore expected to be an incredibly powerful magician. Although Eff is the seventh daughter of a seventh son, all anyone can focus on with her is that she is a thirteenth child and therefore terrible bad luck. One relative even thinks she should be disposed of, and many feel she should be kept away from her twin brother. Thirteenth Child has a strong female character confronted by people who don't want her to succeed. She and her journey towards adulthood are compelling, and the steampunky alternate world has some original characteristics. I did not find Thirteenth Child just another magical coming of age story.
The second book in the series is Across the Great Barrier. Although I enjoyed it, it was a letdown after Thirteenth Child. It did not feel as original and the tension around Eff being a bad luck "thirteenth" was pretty much gone. (This is similar to how I felt with Wrede's Enchanted Forest series - I loved Dealing with Dragons but felt more let down by each subsequent book.) However, Across the Great Barrier kept me interested and I had no trouble finishing it. I definitely recommend the series if you enjoy magical alternate worlds, strong female heroines, and coming-of-age stories.