The historical cost principle states that businesses must record and account for most assets and liabilities at their purchase or acquisition price. In other words, businesses have to record an asset on their balance sheet for the amount paid for the asset. The asset cost or price is then never adjusted for changes in the market or economy and changes due to inflation.
The historical cost principle is a trade off between reliability and usefulness. The historical cost of an asset is completely reliable. After all, that's how much the company paid for the asset. It might not be very useful however. Knowing that a company purchased a piece of land in 1950 for $10,000 does not really tell financial statement users how much the land is currently worth. In this case a fair market value would be more useful. Since fair market values and replacement costs are left up to estimates and opinions, the FASB has decided to stick with the historical cost principle because it is reliable and objective. In current years, the FASB as well as the IASB has become more open to fair value information.
Liabilities are also accounted for using the historical cost principle. When bonds or other debts are issued or received, they are recorded on the balance sheet at the original acquisition price