Solange Knowles Celebrates Big 3-0 ... Bey and Jay Join the Party

Solange Knowles rang in the dirty thirties in a tiny town barely big enough for Beyonce and Jay Z.

Solange, along with 12 friends and family members, spent the weekend in itty-bitty San Patricio, New Mexico on a 2,200 acre ranch ... all for a very reasonable $2k.

Beyonce and Jay Z flew in for the night. The low-key shindig featured a pool party and New Orleans-style catering ... and, of course, Domino's pizza.

And to burn off the calories ... strutting around the White Sands National Monument.

There was also a mini concert ... Solange serenaded guests on a Steinway in the ranch art gallery.

#ShesAllGrownUp