Real photo postcard: Ruins of dam, postmarked April 13, 1928.

On reverse side of postcard is a letter postmarked "GLENDALE CALIF, APR 13, 8 PM, 1928. Has red 2 cents United States postage stamp with portrait of George Washington.

Addressed to: Mrs. A.M. Langly
1421 15th Ave.
Seattle, Wash

Contents of letter:
Glendale, Calif.
April 13th 1928
Well this is the 13th but I am sending you this card anyway. It's a big crime of men to build a structure like that one you see on the other side of this card with a defective foundation built on "Sand." God has said in his word that a house built on sand standith not. 450 min. women and children drowned. dreadfull. hope you are both well. I got your letter.

Seven miles up San Francisquito Canyon Road from today's Copper Hill Drive, construction on the 700-foot-long, 205-foot-high St. Francis Dam started in August 1924. With a 12.5 billion-gallon capacity, the reservoir began to fill with water on March 1, 1926. It was completed two months later.

At 11:57:30 p.m. on March 12, 1928, the dam failed, sending a 180-foot-high wall of water crashing down San Francisquito Canyon. An estimated 431 people lay dead by the time the floodwaters reached the Pacific Ocean south of Ventura 5½ hours later.

It was the second-worst disaster in California history, after the great San Francisco earthquake and fire of 1906, in terms of lives lost — and America's worst civil engineering failure of the 20th Century.