No save the date...invitation only

I would send invites out 3 months prior to the wedding

Is it a destination wedding? If so you will want to give your guests a heads up by sending a Save the Date 8-10 months before so they can book flights and hotels.

If it isn't a destination wedding then 8 weeks before is about the max for sending invites early. Anything earlier you run the risk of guests losing their invite/RSVP card or forgetting about it because they think they have a lot of time to respond. Most people don't know their schedule more than a month or two out anyway, that's why the RSVP by dates are usually 3-4 weeks before and still there are tons of brides that will tell you they had cancellations 1 week to a few hours before.

We are getting married in Iowa and we will have a lot of out of state guests since I am from Illinois, so all of my family is out-of-state. Also, a lot of our friends are from out of state too including the parents of our bridal party.

Since this is considered a destination wedding for a large amount of your guests, I would consider doing save the dates rather than sending invites really early. People will need time to make travel arrangements or request time off work if necessary.

We sent our invites out 3 months in advance.

We didn't send save the dates but mailed our invitations 3 months before the wedding. We had already talked with family that lives out of the area so they were aware of the date in advance. There were no issues with planning for out of town guests.