My mother called a few days ago, opening the conversation with a breathless “I think I’ve found something that might interest you!”

She was right.

Her sister had recently gone through some papers belonging to my late grandfather Elmer Plett, a sober, hard-working dairy farmer who spent the majority of his adult life in the central valley town of Turlock.

Among piles of receipts and newspaper clippings my aunt discovered a mysterious item bearing the handwritten label “San Francisco picture, 1949″. Sure enough, nestled between protective cardboard sheets was a large, glossy, black and white aerial photograph of San Francisco.

The shot is spectacular, taken on an unusually clear winter day. The angle is unusual too, looking almost precisely north towards Mount Shasta — and according to the story of how the photo came to be taken (see below), that view of the distant volcano is what prompted the photographer to take to the air.

What we’re interested in, though, is the city in the foreground — captured in all its hat-wearing, freeway-building, pre-jet-age post-war glory. Take a look:

San Francisco Chronicle aerial photo 1949

click image to view at full size

Beautiful, no?

But my question, of course, is what on earth prompted Grandpa hold on to such a thing? What was his interest in San Francisco? Prior to 1949 he’d made the journey to the big city only once — and that was to visit the ’39 World’s Fair on Treasure Island.

Had he sent away for this photo ten years later to commemorate that event, to summon the memories of crossing the brand new Bay Bridge with Grandma in the old Model A, to recall the Technicolor excitement of witnessing the entire world condensed onto a couple of pancake-flat acres floating in the middle of the Bay?

I’ll never know. Mom has no idea, and neither do her siblings … and dammit, it’s too late to ask Grandpa. So although the possible explanations are limitless, that’s the one I’m choosing. Arbitrary, perhaps — but satisfying.

For your edification — and because Grandpa would have thought that this whole thing was totally cool — I’ve re-typed the sheet of paper (printed by the Chronicle) explaining the photograph. Enjoy …

From 12,000 Feet Up

On a clear day in January, 1949, Chronicle photographer Barney Peterson climbed into a small airplane and circled skyward over the San Francisco Peninsula. At 12,000 feet, his camera lens reached out 250 miles to catch this remarkable shot of snow-covered Mount Shasta (alt. 14, 162). The peak can be seen in the extreme background just a little to the right of center.

Just to the left of Shasta are China Mountain, Cory Peak and Scott Peak, averaging over 8500 feet. To the left of this group is Russian Peak, 8183 feet.

In the foreground may be seen the Spring Valley Lakes and the peninsula communities of Burlingame, Millbrae, San Bruno and South San Francisco. At the extreme right foreground is the San Francisco Municipal Airport. To the left of the airport, in the open space between Millbrae and South San Francisco, is a section of the new Bayshore freeway.

The San Bruno hills are just beyond South San Francisco and to their extreme right is Hunters Point Naval Shipyard. Above Hunters Point may be seen a section of the Bay Bridge and Treasure Island. Above the Bay Bridge in the photograph are Point Richmond and Point San Pablo.

On the extreme left side of the picture is San Francisco’s famous beach, Seal Rock, the Cliff House, the Golden Gate and the Golden Gate Bridge (left center). Short of the Golden Gate Bridge may be seen the street patterns of the Richmond and Sunset districts, divided by Golden Gate Park.

Just north of North Beach sits Alcatraz and beyond Alcatraz is Angel Island. The thin peninsula behind Angel Island is the Tiburon-Belvedere peninsula forming the east shore of Richardson Bay.

The clarity of this photograph was made possible by rare arctic winds which swept the skies of their usual haze. Photographer Peterson used a 5"x7" aerial camera equipped with a 15" Wollensak telephoto lens. The exposure was 1/225 second at an aperture of F/8, using a minus blue filter and Super XX Aero Graphic film.

– Photo Copyright, 1949, by the Chronicle Publishing Company