As it often goes with traditions, we can’t remember how they began. Such is the case in Saginaw, Michigan, where a historic water treatment plant has been lit with Christmas lights for nearly a century.

Since the 1930s, plant employees have pulled lights and a 14-foot wreath out of storage and dressed up the facility and its surrounding grounds for the holidays. Based on stories from retirees and the parents of current employees, that’s the best guess for when the annual lighting display began, says Mark Krawczak, equipment and safety specialist, who has also become a sort of historian for the water plant. Completed in 1929, Saginaw’s water plant was built with both aesthetics and function in mind, and its Gothic architecture is particularly striking when the lights go up each year.

The process begins around October when plant operators go through about 475 strings of lights to make sure the bulbs are functioning.

“It’s the operators on the second and third shifts who often have a little more free time and are able to check the lights,” says Krawczak. “Then near the end of October and beginning of November, it’s time to put them up.”

It takes about two weeks to get everything in place. Krawczak says the lights are stored in numbered totes that correspond to specific areas on a lighting display map, making the task of stringing up so many lights a little more manageable.

“I can remember some years when it was subzero temperatures with 30 mph winds and a blizzard. Of course, that’s when we set up the lights a bit later in the year," Krawczak says.

The lighting ceremony now coincides with a larger community event called Holidays in the Heart of the City, which is held near Thanksgiving. This year the event and the unveiling of the water plant’s display were held Nov. 17. The display stays up through December.

“It changes some year to year based on the trees,” Krawczak says of the configuration of the display. “Through most of the 1990s, we’d go out to one of the local nurseries and pick up 5-foot trees to stake out front alongside the larger trees we had on site. Between some of the landscaping we’ve done and what’s grown or been cut down, we now just need what we already have on site. It’s a good display without having to bring in extra trees.”