Jenna Bush & Henry Hager Wed in Texas

It’s official: Jenna Welch Bush wed Henry Chase Hager Saturday – making her the first daughter of a sitting United States president to marry in 16 years.

The pair exchanged vows just before sundown in a lakeside ceremony threatened by a tornado watch at President Bush’s secluded 1,600-acre Prairie Chapel Ranch in Crawford, Texas.

PHOTOS: See more photos from Jenna Bush’s wedding album!

Pastor Kirbyjon Caldwell, of the Windsor Village United Methodist Church in Houston, presided over the “I do’s” before a 4-foot limestone cross and altar that were the president’s idea for the occasion and will stand as a permanent landmark on the Bushes’ property.

‘A Joyous Occasion’

“This is a joyous occasion for our family, as we celebrate the happy life ahead of (Jenna) and her husband, Henry,” the president said in his weekly radio broadcast Saturday morning. “It’s also a special time for Laura, who this Mother’s Day weekend will watch a young woman we raised together walk down the aisle.”

A source at the ranch told PEOPLE that the president alone, in traditional style, was escorting the bride to the altar. A White House spokeswoman said she did not know if Jenna planned to take the name Hager as her own.

Dinner and dancing for the 200 guests – including family and only the closest of friends, including longtime presidential adviser Karl Rove – were being held under tents.

The Wedding Dress

Jenna, 26, in an embroidered organza Oscar de la Renta gown, was attended by twin sister Barbara, the maid of honor, who wore a dress of moonstone blue shimmer with a silver sash. De la Renta, a close friend of the family, also designed First Lady Laura Bush’s deep turquoise “mother-of-the-bride” gown.

White House spokeswoman Sally McDonough said the colors – from the dresses to the d cor – were selected to mirror the “very natural” colors of the central Texas landscape: the blues of the lake where Bush fishes for bass, the greens of Mrs. Bush’s prized buffalo grass (native grass that she restored to the property) and the lavendar, yellow and blue of the wildflowers.

Henry’s brother, John, stood as Best Man. In keeping with Jenna’s desire for an “organic and natural” feel to the wedding, the men dressed in suits – not black tie. And dancing was accompanied not by a fussy orchestra, but by Nashville-based wedding singer Tyrone Smith, otherwise known as Super T and a favorite at Southern frat parties.

Henry, whose father is a prominent Virginia Republican, celebrated his 30th birthday on Friday amid wedding festivities that included a rehearsal dinner and “Texas-size” afterparty. He met Jenna in 2004, when both of them were working on her father’s reelection campaign.

Finishing up his final year at the University of Virginia’s Darden School of Business, he is expected to get his degree later this month and then begin work for an energy company based in Baltimore, Md., where he and Jenna recently bought a townhouse.

The last time a sitting president’s child was married was the 1992 Camp David wedding of Dorothy Koch, daughter of President George H.W. Bush, Jenna’s grandfather.