"At this point, it's not about me having a passport, it's about them saying I'm not an American," Esqueda said. "And that for me is just the biggest insult I have ever heard."

Esqueda was born in Texas, but was raised in Minnesota. The 30-year-old served combat tours in Iraq and Afghanistan, as a Marine and later as a member of the Minnesota National Guard.

"To serve my country was honestly the greatest privilege that I ever had," Esqueda said.

As part of his service, Esqueda received secret military clearance that only an American can hold. He shared that documentation with the State Department.

Yet, in a 2017 letter, the Department told Esqueda he had not provided a "preponderance of evidence" that proves he was born in the U.S.

In a 2017 letter, the State Department told Esqueda he had not provided a "preponderance of evidence" that proves he was born in the U.S.

The American Civil Liberties Union of Minnesota and the Greene Espel law firm are now representing Esqueda as he appeals the government's denial.

The State Department declined to comment on Esqueda's case, citing privacy laws.

Esqueda and hundreds of others have been forced to defend their citizenship because they were delivered by midwives in south Texas, along the U.S.-Mexico border. They were born at time when some midwives admitted to creating fraudulent birth certificates for children actually born in Mexico.

5 INVESTIGATES traveled from Minnesota to Texas to better understand the government's extra scrutiny on those born along the border and to find the midwife who says he can prove that Esqueda is an American.

View an interactive timeline of this investigation here

'Proof' in Hidalgo

The small town of Hidalgo is planted hundreds of miles from the capitol of Texas, but just a couple miles from the U.S.-Mexico border. It's one of the most southern communities in the Lone Star State comprised of more than 13,000 people, mostly of Latino descent.

Road signs in Hidalgo don't just point to the nearest city, but also to the nearest border crossing where thousands of people cross over from both sides of the Rio Grande River to work, visit family or just to shop.

Esqueda's parents are no different. They're both from Mexico, but lived and worked in Texas when he was born.

Esqueda's father, Pablo, was a truck driver and often spent time away from home. He was on the road the day Esqueda's mother, Francisca, went into labor.

"She had to drop my sister off at the neighbors and she took a taxi herself to go to the clinic," Esqueda said.

That clinic has since moved to a small, plain building with two large signs overlooking the road. One simply states Partos, or births, in Spanish, along with a price tag of $1,600. The other reads, Hidalgo Maternity Center. It's owned and operated by the same man who says he delivered Esqueda.

Roberto Nuñez has been delivering babies in the Rio Grande Valley longer than Esqueda has been alive. He studied to be a doctor in Mexico, but has spent the majority of his life working as a midwife north of the border.

On a hot Thursday afternoon last month, Nuñez agreed to keep his clinic open to look for Esqueda's birth records. He typically closes at 1 p.m., unless he's delivering a baby.

Speaking in a blend of Spanish and English commonly referred to as Tex-Mex in the Rio Grande Valley, Nuñez says those births are few and far between these days. Instead they've been replaced by requests for birth records.

"I have a list of maybe a hundred people that, que han venido por el (who have come for the) paper," Nuñez said. "The record."

He has a faded, handwritten note taped to the glass partition at the front desk requesting $125 per copy of birth records.

In a small back office where he regularly shares lunch with his wife, Nuñez keeps meticulous records including birth documents of an estimated 5,000 patients dating back to 1987.

Each folder is neatly labeled with the month and the year of delivery. It took him just minutes to find the folder titled September 1988 that held Mark Gilbert Esqueda's records - baby number 430.

"Proof," Nuñez said. "I got it."

Each folder as part of Nuñez's records is neatly labeled with the month and the year of delivery. It took him just minutes to find the folder titled September 1988 that held Mark Gilbert Esqueda's records - baby number 430.

Most of the information relates to Esqueda's mother's condition at the time of his birth, but it clearly shows where and when he was born. Most important is the name at the bottom left corner of the paper, which reads, "Police Officer: Roberto Dominguez."

Thirty years ago, Nuñez says he knew that the citizenship of the children he delivered would one day be under suspicion. That's because some midwives in south Texas admitted to falsifying birth records for people actually born in Mexico, according to a 2009 federal lawsuit.

Nuñez was not part of that case, but says he heard rumors of midwives committing fraud early on in his career. To protect his name and business, Nuñez went to the City of Hidalgo to create a witness program with the police department.

"In each delivery they came here to…see the patient, you know…the belly," Nuñez said. "And then they come again to check the baby, the umbilical cord…pues (well) the little one."

That police officer would then sign off on the mother's birth records as a witness, including Esqueda's. The police officer's own witness report would then be filed with the Vital Statistics records of the City of Hidalgo.

Robert Nuñez created a witness program with the Hidalgo Police Department after hearing rumors of midwives falsyifing birth records. He would call the police to verify each birth at his maternity center.

It's not just former patients asking for those records. A separate folder holds the business cards and letters from Homeland Security agents and Texas state investigators who asked Nuñez to review birth records of those they suspected of not being Americans. Nuñez says he has nothing to hide.

In fact, state investigators have looked into two people delivered by Nuñez that they suspected of being born in Mexico. Documents from the Texas Licensing and Registration Department show those claims were unfounded.

"OK, come in, my clinic is open," Nuñez said, gesturing around his clinic. "Everybody is over there. Everybody."

Although Nuñez has spent his life delivering babies and keeping detailed records, he says the scrutiny has taken its toll on his business and other midwives.

When asked whether other midwives area also under suspicion, Nunez nodded and said, "Si (Yes). Same problem. Every midwife in the border, near the border – they got the same problem…Everybody! They are targeting everybody…"

Preponderance of evidence

Esqueda's story isn't unique to folks in the Rio Grande Valley. More than 60 miles east of Hidalgo, one attorney has taken the federal government to court an estimated 150 times over this issue.

Jaime Diez has spent 20 years working as an immigration attorney in Brownsville. It's one of the largest cities along the 1,254 miles of shared border with Mexico.

Diez says the government puts the onus on the person applying for a passport to provide a "preponderance of evidence" to prove their citizenship, meaning they more than likely were born in the U.S. However, Diez says the standard changes depending on where a person is born.

"If you were born in south Texas, there is a likelihood you were born in Mexico," Diez said. "If you were born in Kansas, there is no likelihood that you were born in Mexico, so they only require a document."

Because of that, Diez says everybody born in south Texas "is under suspicion." As a result, he says more people are walking into his office asking for help to defend their citizenship and get their passports.

However, in a statement to 5 INVESTIGATES, the State Department says its domestic passport denials are at the lowest rate in six years.

Yet, Peter McGraw, an attorney with the Rio Grande Legal Aid office in Brownsville, says his office has recently seen more cases of the State Department requesting additional documentation from people applying for their passports.

"Even though the government kind of takes the position that we're not really challenging your citizenship, they are interfering with your right to travel," McGraw said. "…and in a lot of cases that I've seen, they're interfering with the right to travel with pretty flimsy allegations."

Both McGraw and Diez say the State Department's requests are often burdensome on those applying for passports.

"We're talking about, you were denying somebody the right that he was born with. It should be an apology," Diez said. "They should be saying, I'm sorry we made you spend the money…sorry that we questioned you, we're going to learn from this so that we don't put anyone through the same situation."

Proving he belongs

Hundreds of miles north of Texas, Esqueda points out the pictures of his sister's children on the walls of his home in Heron Lake, Minnesota. They were born overseas on U.S. Army bases in Germany and Italy, but because Esqueda was denied a passport, he missed their births.

"I wanted to go and obviously see her and also maybe see the country," Esqueda said. "I wasn't able to go and only my parents went."

He now hopes his birth records will be the piece of evidence that will verify what he has known all along.

"I have never had any doubt that I was born here," Esqueda said. "But I'm glad that this shows more."

He says he worries that if the government can challenge his citizenship for a passport, they could do the same for other benefits, like Social Security.

It's also personal for Esqueda who says he has spent his entire life trying to prove he belongs in the U.S.

"I really want to make them feel shamed for having to put me or anyone else through this when they know they do not have to," Esqueda said.