I have heard that one of the strongest memory stimulators is your sense of smell.  A fresh-out-of-the-oven apple pie will bring you back to the days when grandma was baking them and you were a little kid.  A certain perfume will arouse the memory of a long-ago love.  A smell can take you back to a familiar place, too.

I was the son of a sailorman;  I grew up next to an ocean, a few different ones, in fact.  The smell of salt spray will bring up a variety of memories, depending on my current mindset.

Different places have different smells, some are unique.  Just south of us is a city they call the "Steel City" and the southern part of the city smells like the steel mill a lot of the time:  hot and metallic, like a furnace, sooty and gritty.  We lived in Mannheim, Germany years ago and there was a sawmill there that had a distinctive smell;  we used to call it the "tunafish sandwich factory".   The motor pool at Turley Barracks smelled like diesel smoke and icy mud.  Waking up in the woods of Germany you are greeted by the smell of fresh turned earth (courtesy of the tanks and other tracked combat vehicles), fresh mud and broken grass and trees.  These smells come home with you, along with the stale odors of over-used socks and underwear and the faded mothball smell of dirty field equipment (which MamaCharlie would not allow into the house...I had to strip off the funky stuff on the back porch).  Across the river from Mannheim is the city of Ludwigshafen which has a huge chemical plant and it smells nasty, but nasty like no place else I 've ever lived.  While on the subject of Germany's smells...all over the country in late fall, huge markets are set up in cities...they are called Kristkindl Markts, and the aromas that mingle there are like no where else:  spiced hot wine, burnt sugar coated almonds, grilled bratwursts, and of course...beer. 

Old Town San Diego always smells like spicy Mexican cooking;  just outside of Canon City, Colorado is a huge prison complex where they make tortillas and you can smell them out on the freeway, a mile away.  The Navy base at Norfolk, VA always smelled like fuel oil and smoke and the huge consolidated mess hall; greasy and oniony.  Los Angeles smells like smog...a kind of chemically, stinging smell...even when the wind blows the smog away,  it is a permanent part of the background there.  Saigon used to smell like hot oil and noodle soup and car exhaust...and often like cordite. 

On our trip last month we commented on how some places always smelled the same.  La Jolla smells like "California"...palmy, sandy, salty, and misty warm.   Plaster City smells like plaster, go figure.  Yuma smells deserty, and the desert smells like sage and dry ground.  After a rain, the desert smells so full of plant and grass smells it surprises you.  Monterey smells like the ocean and fog and Fisherman's Warf.  South Phoenix used to smell like a feed lot, as did Chicago, Kansas City, Denver, and lots of other western towns; but Phoenix's air was mixed with the scent of the Japanese flower fields growing southeast of town (Where have all the flowers gone?  Gone to freeways, everyone)    Most of these places get their smells from what is going on there.

Then there's hospitals, hospices, and old folks' homes. A mix of anticeptic, urine, alcohol, bleach, and despair.   Slaughter house and rendering plants are awful, as are crime scenes or battlefields.   All have an odor that brings them to mind when your nose detects it. 

From the salt-spray air of California to the wet-sage smell of the Arizona deserts, to the fresh-snow iciness of Colorado (except for Greely that still smells of manure and feedlot ammonia), our noses brought us memories and recognition of our surroundings.  But there was one place that was unique.  Stanfield, Arizona just outside of Casa Grande, smelled like an over-full dirty diaper.  What the heck was going on in Stanfield???