There are 1.06 quarts in a liter. The volume of a liter is defined as 1 cubic deciliter. At 4 degrees Celsius, 1 kilogram of water has the volume of 1 liter. For cooking purposes, Betty Crocker considers the quart and liter to be equivalent.
The United States is one of three countries that have not yet adopted the metric system. Instead, it uses a system based on the English units that were in common use when the United States declared its independence, and these units include the quart. Approximately 50 years after American independence, Great Britain revised its system of measurements to change the definitions of some units, causing discrepancies between U.S measurements and imperial units. In 1893, the Mendenhall Order redefined most of the customary units that the United States uses in terms of the metric system. The International Yard and Pound agreement of 1859 made further refinements of the U.S. system.
The Omnibus Trade and Competitiveness Act of 1988 makes the metric system the preferred system for trade within the United States, but it allows for voluntary compliance. It says the government is responsible to assist industry in the conversion. Manufacturers commonly list both customary and metric weights and measures on their products, but they prefer using customary units, while those in science and medicine favor the metric system.