Traveling alone to Green Bay and Door County is considered to be quite safe. The locals are generally friendly and helpful. Green Bay is a small city and Door County is more rural with plenty of tourist-friendly shops, hotels, and restaurants. Both places are quite welcoming to travelers, with low rates of violent crime, especially in the areas frequented by tourists. However, just like anywhere, be mindful of your surroundings, especially at night, and don't leave your belongings unattended.