From their origin, the colonies struggled with the development of an effective medium of exchange for goods and services. After depleting the vast majority of their monetary resources through imports, the first settlers strained to keep money in circulation. They could not find a suitable medium of exchange in which the value did not depreciate. The colonists generally employed three main types of currency. The first was commodity money, using the staple of a given region as a means of exchange. The second was specie, or gold or silver money. Lastly, paper money (or fiat money), issued in the form of a bill of exchange or a banknote, mortgaged on the value of the land that an individual owned.