Complex sentence: The settlement was founded in the former Timucua village of Seloy, and to this day, the locals of St. Augustine claim that it was here that Menéndez held the first Catholic mass in what is now the continental United States.
Split into simpler sentences: The settlement was founded in the former Timucua village of Seloy. To this day, the locals of St. Augustine claim that it was here that Menéndez held the first Catholic mass in what is now the continental United States.