The scenery reminded me of what Big Bend National Park ranger Michael Ryan told us hundreds of miles before we reached this part of the southern border.
"It's not just one border," Ryan said. "It changes, depending on where you are."
Ryan has lived along the southern border for nearly 30 years. But after a nearly 2,000-mile journey from south Texas to where the southern border reaches the Pacific Ocean, it seemed like Ryan's words just don't refer to the physical changes.
The southern border is a dynamic environment, culturally and environmentally. It's constantly evolving.
Uncertainty in the borderlands
Pedro Rios leads the San Diego chapter of the American Friends Service Committee, a social justice organization focused on helping immigrants in southern California. Rios says the beginning of the Donald Trump presidency has ushered in the next new era of uncertainty for the borderlands.
"There's a lot of tension," Rios said. "A lot of fears, because in the past, when the border becomes a target, it's an excuse to increase enforcement, (and) the people who live on the border suffer."
It's here in this southwest corner of California where the San Diego metropolitan area hits the Mexican border where the dramatic changes of the border are crystal clear.
On the other side of the border is Tijuana, a sprawling and vibrant city of 1.3 million people. Residents say in recent years the wait times to cross the ports of entry into the United States can take as long as 5 hours on some days.
This section of the U.S.-Mexico border is one of the most heavily fortified sections where the border wall has been doubled up in some places. But here, Homeland Security agents are battling smugglers -- not just above ground but below ground as well.
The San Diego sector is home to a band of Border Patrol agents known as the "Tunnel Rats." This team specializes in uncovering and investigating underground tunnels used to smuggle massive loads of drugs into the United States.
Lance LeNoir, a US Border Patrol operations officer leading the sector's "Tunnel Rats" team, is taking our CNN crew deep inside one of these tunnels.
"The imagination of people trying to come north is something I don't try to second guess. (It is) incredible some of the methods they use," LeNoir said.
To reach the bottom of what's known as the Galvez tunnel, we take a series of four steel ladders straight down a 70-foot shaft.
When we reach the bottom, the air is muggy and one of the first things you see is a makeshift distance marker humorously telling you that Mexico is 8 feet to the south and San Diego is 40 miles to the north.
The Galvez tunnel was discovered in 2009. It was dug from a warehouse that we can see just beyond the border fence and extended about 760 feet to the north toward another warehouse on the US side of the border.
LeNoir said the tunnel was never fully completed, but it speaks to the ingenuity and brute strength used to dig these tunnels under the border walls. The tunnel was cut through jagged rock and measured about 6 feet tall and 4 feet wide.
"They (drug smugglers) are looking for bulk transport," LeNoir said.
This tunnel was equipped with a rail system and electricity. The agent says the tunnels are usually used to move massive loads of marijuana and cocaine.
"We recognize digging crews," he said. "They all have their unique shape, size and little nuances that you pick up."
Juan Munoz, Homeland Security investigations special agent, says in the last 10 years nearly 30 tunnels have been discovered in the San Diego area alone.
Munoz says these tunnels are usually found connecting between commercial warehouses, but that to discover these tunnels requires intense investigative work and intelligence information.
"They will continue to go on between the Mexican and US border," Munoz said. "If there's a way that these drug trafficking organizations can stay undetected, and it's by tunneling, they will."
LeNoir says the tunnels have grown more sophisticated as border security above ground as become more elaborate and extensive.
"This is usually high dollar-high risk reward enterprise," Lenoir said. "It's a lot of stuff that they have to move in a small amount of time."
But as the arsenal of border security tools has grown and appears that it will grow even larger during the Trump administration, border residents worry about the toll this will take on their communities.
Alicia and Chris Martin live on the US side of the border and have businesses on both sides. They own La Roca restaurant in Nogales, Mexico -- south of Tucson and near the Arizona border. In addition to their restaurant, they own organic farmland in Mexico and a produce distribution business.
They have seen how the charm and simplicity of border life has slowly eroded away.
Alicia Martin recalls the days, as a young girl, when a group of friends would freely run across the border to buy ice cream from a vendor on the Mexican side of the border.
"We would just walk across, wave at the guy and go back. That's it," Alicia Martin said. "So this thing of a line. A border. A fence. A wall. I mean it doesn't compute for us."
Those days are long gone, and the Martins know it's not coming back either.
The US State Department warns that the Mexican state of Sonora, which includes Nogales, is a "key region in the international drug and human trafficking trades," and encourages American citizens to limit travel to main roads during daylight hours.
But the Martins stress that the neighborhoods around their restaurant are safe, and say that because the borderlands are often painted as a wild and dangerous place it hurts development and growth.
After September 11, when border security became a higher priority, the Martins say intensified immigration controls and the fear of border violence dramatically effected tourism to Nogales.
"It was like somebody came in and flipped a switch. There was nobody in town," Martin said.
La Roca struggled to keep its doors open. Alicia Martin's uncle opened the restaurant 45 years ago and the thought of going out of business was painful. The couple held on and now they're starting to see business and the energy of this border town come back to life.
With diplomatic tensions between the Trump administration and the Mexican government starting to escalate, the Martins worry about what will happen next.
Chris Martin argues that throwing up trade barriers, dismantling NAFTA and building walls will only bring back more depressing days.
"They are such harsh approaches. You are treating a symptom," Chris Martin said. "It's education, it's economic security, it's economic strength that is going to keep people from migrating in droves from one country to another."