What's the biggest cultural divide in our fair city? Is it natives vs. new comers? Leftists vs. ultra-leftists? Tech people vs. everyone else? No, it's much deeper.

Ice cream.

Yes, that cool childhood treat is the true issue that keeps people up at night in San Francisco and causes passionate debate into the small hours. In some homes, it may even end marriages. Once again, San Francisco is ruled by a big four: but this time instead of Stanford, Huntington, Crocker and Hopkins, it's Swensen's, Bi-Rite, Mitchell's and Humphry Slocombe. What does your ice cream allegiance say about you? Can your heart belong to more than one parlor? And what about mixed relationships: could a Bi-Rite Cheesecake Blueberry Swirl and a Humphry Slocombe Cinnamon Brittle ever make a go of it? What about a Swensen's Swiss Orange Chip and a Mitchell's French Custard Vanilla? How would they raise the children? Here's a rundown of everything you need to know about the big four in the ice cream wars. There's just something so perfectly San Francisco about waiting in line outside for forty minutes on a bone-chilling, foggy night for a scoop of one of your favorite local flavors.

Swensen's

1999 Hyde Street

Since: 1948

History: The first Swensen's on Russian Hill begat franchises throughout the United States and beyond, but for long-time San Franciscans nothing compares to hearing the ding of the cable car while enjoying a sundae at the original. Most San Francisco kids have memories of visits to the parlor and judged juvenile birthday parties by whether or not cake time included a scoop of hand-packed Swensen's Thin Mint or Midnight Brownie (Lord help the child whose parents went to Baskin Robbins).

Ice Cream: Earle Swensen was fond of saying he sold ice cream as "good as father used to make" and, although a lifelong vanilla man himself, went on to supervise the creation of over 150 Flavors during his lifetime. Classic sundaes with lady finger wafers, butterscotch sauce topped scoops and banana splits with hot fudge are the staples: this is a strictly old fashioned ice cream parlor and proud of it.

Notable Flavors: Swiss Orange Chip, Rum Raisin, Bubblegum (as a connoisseur of bubble gum ice cream I can say, as far as pink bubble gum flavors go, this is the one to beat), Macadamia, Strawberry-Banana Swirl, Sherbets Orange, Lemon and Lime (authentic recipe-hasn't-changed-since-the-sixties Mad Men punch bowl style sherbet).

Parlor Vibe: A neighborhood institution, as Russian Hill has changed over the years the parlor's griege and orange color scheme and checkerboard floors have remained unchanged. Many (if not all) of the original fixtures and ice cream tools remain making the chocolate malts lumpy like every San Franciscan knows they're supposed to be.

Patrons: Natives, neighborhood regulars, private school kids crossing over from Pacific Heights in the afternoon, tourists wanting an authentic taste of old San Francisco, people old enough to remember when ice cream wasn't a city wide debate.

What it says about the fan: For Swensen's fans, ice cream isn't a trend or a foodie hobby: it's dessert. Most old city dwellers have a go-to flavor they can instinctively describe no matter how long it's been since they last had it. You'd call Swensen's ice cream nostalgic if it wasn't such a consistent flavor on the city's palate.

One of the City's Best: Swensen's was such a neighborhood iconic by the 1970s that author Armistead Maupin frequently mentions the parlor in his Tales of the City. Heroine Mary Ann Singleton enjoys a scoop of Swiss Orange Chip in the first book in the series and opens her return to San Francisco in Mary Ann in Autumn with a trip back to the old Barbary neighborhood for the taste of the treat she loved in her twenties. Only in San Francisco does ice cream take the place of the Proust Madeleine when it comes to evoking memory.