Jim Phelan is the golden fire hydrant in the Mission. He’s the Lady of Stow Lake. He’s the parrots of Telegraph Hill.

He’s a San Francisco legend, just one that’s never been told.

The native San Franciscan is a third-generation steeplejack — a centuries-old profession that you’ve very likely never heard of, and even more likely never seen in action.

“There’s a few of us, but not a lot,” says Phelan, 67. “You know what, the average person here, even 1 out of 100 wouldn’t know what a steeplejack is.”

Today, standing inside San Francisco’s Ferry Building, and armed with Wikipedia and San Francisco’s longest-tenured steeplejack, I will understand in great detail what a steeplejack is.

And that’s very literally a guy (jack!) who climbs steeples (steeple!), or really any building that may have something atop it that needs fixing. In the pre-crane era, it was the only way to get a flag unfurled, or a broken window fixed, or a piece of mason work retouched. In the post-crane era, it’s the cheaper way to do any and all craftsman work (or half-staffing of flags) at some of the most hallowed structures in the United States.

Using a combination of blocks, pulleys, ropes, and a far greater understanding of physics than pretty much everyone, Phelan has used the “old-fashioned way” of reaching the precipice of everything (seriously, look at the back end of the slideshow for photo views you won’t believe) from UC Berkeley’s Campanile and the National Archives in Maryland to nearly every sports facility in the Bay Area — past (Candlestick Park) and present (AT&T Park, Levi’s Stadium) — and really any San Francisco building of significance.

That includes the Ferry Building’s clock tower, a 121-year-old building that has only two people inside of it during the year: the clockmaster, who goes in twice a year to change the time, by hand, for daylight-saving time, and Phelan, who spends a day inside the postcard-worthy edifice twice a month on average.

Outside of them, only a handful of people have been inside of the clock tower ever, and — as I find out as we make our way through the “Clock Tower Access” door — all of them have signed their names inside of its walls.

There are names with the year 1906 inscribed alongside them (“there were a lot of people in here right after the earthquake,” Phelan says), there are signatures from virtually the entire Phelan family (his sister, niece, and even his Oakland firefighter nephew, all of whom are also steeplejacks, even if part time in some cases), and even one newly engaged couple from the '80s. There’s “Rutherford - took all the Redwood from old water tanks” in 1967, there’s “Selvin Guevara,” who helped Phelan hang the World Series champions banner outside the Ferry Building in 2012, and, because at least one person had a sense of humor, “Chris Columbus, 1492.”

The signatures are varying degrees of faded, but all largely legible inside of the concrete walls, which keep the interior a nice breeze-level cool.

Not unlike the interior of the Golden Gate Park’s windmills, the clock tower’s insides are mostly a structural marvel, from the original diagonal bracing (which was intended to stiffen up the tower in the wind, but Phelan believes that kept it upright in the 1906 earthquake), to the staircases that get steeper and shallower the higher you go.

The crown jewel, though, is seven very high-ceiling-ed stories up, where we exhaustedly find the actual clock mechanism.

And it’s beautiful.

A dark forest green base (with intricate hand-painted flourishes on each of four legs) holds up a working clock that is entirely smaller than anyone would expect. It’s maybe 5-by-5 feet in total, has dozens of gears that emanate a loud-ish buzzing, and sit inside of a padlocked room in the middle of the floor.

There are digits written on the wall for what presumably used to be the number you’d call for the time, and a busted landline sitting at the foot of the clock mechanism.

Outside of the tiny room, you can see part of the backside of all four exterior clock faces, with tiny ladders leading to a little cubby positioned behind each.

Phelan stands in front of one of them, a tall, gangly man with dad jeans, and a Ferry Building polo. His curly hair spills out both sides of his Giants cap, as he motions to the inside of the clock face. Previously, there were light bulbs that went around the clock face, and these hatches were used to access and replace them.

We spot the wall Phelan signed his name on right after the 1989 Loma Prieta quake, when he helped the Marines remove the bent flagpole from atop the clock tower, and Phelan is a little surprised — he didn’t remember if and when he had signed the wall after so many years inside of the building.

Jim isn’t the first Phelan to make his way through the building either. His dad, Jim Sr., worked inside of the clock tower up until the late '90s, and before that, worked with Jim’s grandfather, John, learning the trade. John Phelan was a steeplejack contractor in Massachusetts in the 1920s and '30s.

Both Jim Sr. and Jim Jr. were also iron workers, Jim Jr. on the Bay Bridge for 12 years where he earned the nickname Spider-Man.

“I was really reckless; I remember jumping beam to beam, and one day I slipped and caught myself with my hands,” says Phelan, who grew up in Bernal Heights (“they used to call it the Mission”) and proposed to his wife atop the Golden Gate Bridge. “The most important quality when you have this job is to be able to respond with a quick mind. Something goes wrong, you don’t have time to think about it, it needs to be instinctive. We’re tied off all the time now, but decades ago we were free climbing everything.”

Jim and I continue our ascent, first to the floor that houses the massive speakers that provide the clock tower chime at the half hour and hour every day, and then to the final floor Ferry Building officials will give me access to (any higher, and I’d be inside the glass dome). And that’s where I see what Jim sees every day: the view.

It’s incredible how you can make your way through the same city day in and day out and still be taken aback by seeing it from a different perspective — in this case, one of the most incredible ones, seen from the equivalent of 27 floors above the waterfront.

Phelan says it’s the reason he still loves his job today, as does his son Kells, a San Jose State undergraduate who has been working alongside dad during summers and weekends since he was in his early teens.

“It’d different every time — it’s not the same spot, it’s dynamic,” says Kells Phelan, who’s technically now a fourth-generation steeplejack. “Growing up, it was always super interesting, always really unique. It was one of those jobs that no one could relate to so I wanted to do it more.”

Jim Phelan flashes me his iPhone background — it’s of Kells atop a light pole at Candlestick Park. To call Jim proud of his colleague and son would be the understatement of all understatements. He beams when the subject of Kells comes up.

Just before it’s time to head back down, the clock tower chimes begin blaring. It’s 10:30 a.m.

And inside the clock tower, there’s no forgetting it.

Grant Marek is the Editorial Director of SFGATE. Email: grant.marek@sfgate.com | Twitter: @grant_marek