Noticing some high 5-digit street addresses, started wondering if there are any six-digit addresses. This blogger explored the question thoroughly. There are three fairly systematic six-digit setups.
1. Florida was first, with the numbering along US 1 to Key West. The street numbers start at Key West and run over a hundred miles northward, so addresses in the 101000 range are common at the north end. Florida then continued six digits on various country roads.
2. The Olympic Highway here in Wash has the same kind of mile-based numbering for its whole length, with some 234000 numbers near one end.
3. Oklahoma’s county roads use a similar mile-based routine, with many six-digit numbers.
Those seem to be the only examples. Many places have five digits on county roads, but most of them break the sequence before it can reach six. A house my parents rented in Bowling Green was 12345 Gypsy Lane, while the houses just north of it, inside the city limits, were only three digits like 805.
Polistra's Mill 