Strings of golden light blaze across an ink-blue bay as the San Francisco–Oakland Bay Bridge soars toward the glittering city skyline — this linen-era nighttime view is one of the most dramatic postcard images of 1930s California infrastructure, and this particular example carries a double rarity: it was postmarked October 2, 1939 with a Golden Gate International Exposition machine cancel, tying it directly to the legendary world's fair held on Treasure Island in San Francisco Bay. The sender, a woman named Martha, writes with warm urgency to a colleague named "Mrs. M.S." at the Bureau of Mines, Department of the Interior, Washington D.C.: "Everyone has asked about you — even the veterans on this street (nearly)! Sorry not to see you before I left but was rushed at last minute — Will be glad to see all of you again." A government employee on assignment to the 1939 World's Fair, sending regards back to her colleagues in the capital — a vivid human thread woven through one of America's great civic spectacles.