Throughout history, societies have established systems of law to govern the behavior of citizens, regulate their interactions with each other, and mediate disputes. One of the earliest known codes of law is the Code of Hammurabi, which was developed about 1760 B.C. by the Babylonians. Roughly 350 years later, Moses was given and then introduced the Ten Commandments, which have become the foundation of Judeo-Christian ethics and the basis of our current legal system. The ancient Greeks and Romans set up the first schools of law for young boys to learn the many skills (especially public speaking) required for successfully pleading a case. The Greeks placed great emphasis in their training on thinking logically, another important part of debating and proving matters of the law.

During the next 2,000 years, cultures throughout the world developed oral and written laws that established rules for commerce, that governed human behavior, and that mandated penalties for a variety of offenses such as murder, theft, and sexual infidelity. In western civilization, examples include:

• Byzantine emperor Justinian’s Body of Civil Law (529–565 A.D.)
• King Ethelbert of Kent’s “Dooms of Ethelbert” (604 A.D.), the first written code of laws created by an Anglo-Saxon king
• Ireland’s Brehon Laws (600–700 A.D.), the official compilation of ancient Celtic laws dating back to 2300 B.C.
• common law (1066 A.D.), a system of laws that was derived from court decisions based on specific cases (as opposed to civil law, which is based on a code of laws created by legislatures and rulers)
• the Napoleonic Code (late 1700s–early 1800s), in which the French emperor Napoleon organized and refined existing European law

In early America, settlers lived under the English common law that they brought with them to the New World. American judges became major creators of law through hearing cases and making decisions. They followed the English principle of precedent, or stare decisis (Latin for "to stand by a decision"), using previous court decisions as rules to guide subsequent ones. This common law was later modified by the Articles of Confederation and Perpetual Union (1781) and then the Constitution (1787).

Most early lawyers were jacks-of-all-trades. They would argue cases in court, both criminal and civil, and they might represent either party in a dispute. They would also write contracts, draft wills, handle domestic disputes such as divorces, and take on any other legal tasks.

Colleges and universities in pre-colonial America did not teach law. Lawyers tended to come from wealthy families, and the wealthiest families sent their sons to London to study law at the Inns of Court. Others who could not afford such a luxury would earn a degree in some other subject, such as philosophy, and then read law with a practitioner. The aspiring lawyer in a quality apprenticeship would spend his time studying cases, doing research, drafting documents, and performing other tasks that prepared him to practice law on his own. Eventually a new lawyer would be admitted to the state bar and allowed to seek his own clients. Bar admission standards varied greatly among states.

In 1779, the first law school in the United States was established at William & Mary College in Williamsburg, Virginia. The second-oldest law school was the Litchfield Law School in Litchfield, Connecticut. It was founded in 1784, and more than 1,100 students attended the school before it closed in 1833. In the following decades, other law schools were established, including those at the University of Pennsylvania (1790), University of Maryland (1816), Harvard University (1817), and the University of Virginia (1819).

In the early years of law practice in America, with different educational and bar certification standards in different locations, levels of professionalism among lawyers varied greatly. This began to change in the late 1800s. In 1878, the American Bar Association (ABA) was founded to create uniform academic standards and rules of conduct for lawyers. In the 1890s, the ABA urged state bars to establish rules for admission that required attorneys to have earned an academic degree in law. Around this time, many new colleges and universities opened throughout the United States, and many of them also opened law schools. The length of law education was extended from two to three years, and admission standards were raised. The American Bar Association began accrediting law schools in 1923; it accredited 41 schools that year. Today, more than 200 academic institutions are ABA approved.

The ABA’s efforts to regulate the legal profession increased the quality of practicing lawyers while screening out many unqualified individuals. The number of law school graduates remained relatively stable in the two decades after World War II, producing a steady but not overwhelming supply of new lawyers.

That changed in the 1960s and 1970s. More people—men who had gone to college with the help of the G.I. Bill, the educated children of baby boomers, and especially women and racial minorities—became interested in becoming lawyers. From 1969 to 1975, 22 more law schools were accredited by the ABA, and the number of lawyers increased rapidly. This employment growth continued into the 1980s: By 1981, membership in the ABA increased to 255,000—growth of about 189 percent from 1952.

In the late 1960s and early 1970s, lawyers adopted the practice of hourly billing, which increased earnings and created an atmosphere that prompted growing specialization in the legal industry. Competition for clients also increased. Demand increased for lawyers who had the ability to attract business (known as rainmaking), and these attorneys received high salaries and excellent benefits. 

The legal field has changed dramatically during the past few decades. Technological advances now allow lawyers to conduct electronic discovery, work remotely, and communicate with clients and colleagues at any place and time. Paralegals handle many basic legal duties, and some tasks are even outsourced to workers in foreign countries. The Great Recession (December 2007–June 2009) and the COVID-19 pandemic forced many law firms to close or merge, and many remaining firms reduced starting salaries for new law school graduates and offered fewer partner-track positions. In response to client complaints about high pricing and growing competition for clients, approximately one-third of law firms are using alternative billing methods. The number of nontraditional providers of legal and legal-related services continues to increase, which has reduced market share for law firms. Despite these developments, legal careers remain popular, and often rewarding, options for young people, and top lawyers still enjoy excellent pay and steady employment.