Where in the US can one have a farm/garden without irrigation?

[Hollytree]

I don't water my garden much and it's pretty lush.

[Arktikos]

My two locations. 1st, SE AK. Not many crops do well in SE Alaska unfortunately, due to lack of sunshine. Our longest recorded period ever without rain is 21 days, even 1 week without precipitation is uncommon. Summer is not a dry season like it is in PNW.

Puna, Hawaii. Extended dry periods can occur here, despite high annual rainfall. (150 in.) However, I've had an orchard of tropical fruits that enjoy/require a lot of rain and have never had to irrigate in over 25 years. Fingers crossed! I still worry about a bad drought hurting trees some day, because the soil is thin. An even better place in Hawaii would be the Hamakua coast, as mentioned by a previous poster, because the soil is deep there.

In Alaska? No worries! My grandfather was a Wisconsin potato farmer for decades. I remember his comment when visiting here, looking out at yet another rainy day: "You would never have to worry about drought". Potatoes actually do grow fine here.

[Serious Conversation]

I'm from northeast TN. I've gardened recreationally/on a small scale, and aside from occasional watering, it's not usually needed.

It tends to rain more in the higher elevations of southwest VA and western NC. I highly doubt you'd even need to water at all most years.