It does depend on each child's maturity level.
I have 6 children - ages 20 thru 12 - and the earliest Iv'e allowed any of my children to stay home alone was 13 yrs old. We've known some of our neighbors for over 8 yrs. and my children know whose house to go to in case of an emergency.
My 20 year old was the youngest minded of all - around 16 yrs. old was told to stay home and keep house while we went shopping/pay bills, we came home to open doors (literaly open doors - screens and main doors), while he was down the street and out of view of our house, playing b-ball at the playground court. He told us he was airing the house out because he tried to bake a frozen store-bought pizza, on the racks, with the cardboard still under the pizza!
My husband's family was in the habit of allowing my oldest, aged 11, to watch his siblings ages 10-5, while we were going thru all the negativity. Once they told me they found all of them outside and down the street with the front door open. CPS was helping me out and they were told by my children what happened. That's when Family Services and CPS planned for me to move from Virginia to Kentucky. I made the move to Indiana.
Children on their side of the family are allowed to stay home around 10 yrs old and they take their first bus ride downtown by themselves (after being shown at least 2-3 times), and they catch it back home also.
So yes, it does depend on each child's maturity level.