Listen to shat progodyssey says. In addition, inspect your neighbors' run-off as well. I've seen residents in neighborhoods with old homes, built right next to each other, angle their gutter drains and run off into the next-door neighbor's property. Keep in mind, the current residents may not know their gutters are running into your property. It could have been that way for many years.

>_TEOTWAWKI_
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>I'd like to second what _TEOTWAWKI_says. However, I would emphasize checking the crawl space to see if a moisture barrier is present. If the crawl space is just exposed soil, that's likely your main source. Moisture will evaporate into your home during warming periods and when the house is heated. As a minimal expense test, I would recommend buying a moisture barrier and stretching it over the exposed soil below the crawl space and making sure all gutter drains and surrounding foundation slopes exit away from the house and crawl space and cannot pool.