A lifelong resident of Rockwall County near Dallas, Hall served as a carrier pilot in the Navy during World War II. He attended Texas Christian University and the University of Texas, and received a law degree from Southern Methodist University. He was elected county judge (chief executive) of Rockwall County in 1950 and served until 1962, when he was elected to the Texas State Senate and served two terms. He then entered private business until 1980, when he was elected to Congress in the closest race in the district's history, winning by only 4 points. However, he has never faced another election nearly that close. He has been reelected 12 times without serious opposition, never dropping below 55 percent of the vote.

Hall was originally elected as a Democrat. However, he described himself as "an old-time conservative Democrat," and was one of the most (if not the most) conservative Democrats in the House for many years. He was an early supporter of a constitutional amendment requiring a balanced federal budget and also favored legislation requiring a super-majority on any tax increases. He frequently clashed with the Clinton administration, and voted for three of the four articles of impeachment against Clinton. He endorsed George W. Bush for president in 2000; the two have been friends for many years.

Hall's conservative voting record can be explained by the demographics of the 4th District. It had once been reliably Democratic, but became increasingly friendly to Republicans as Dallas' suburban growth reached into much of the district. The 4th has not supported a Democrat for president since 1964. By the 1990s, Hall was the only elected Democrat above the county level in much of the district. In some areas, he was the only elected Democrat period. Nonetheless, he never had any real difficulty being reelected; he won 10 more terms as a Democrat with an average of 60 percent of the vote. Nonethless, it was virtually taken for granted that a Republican would win the seat once Hall retired.

He was frequently rumored as a candidate to switch parties, especially after the Republicans took control of the House in 1995. Even as Democrats with far less conservative voting records switched parties, Hall insisted he would remain a Democrat if as it did not hurt his constituents. He felt that he had an obligation to "pull my party back toward the middle." He was one of the co-founders of the Blue Dog Coalition, a group of moderate and conservative Democrats.

Hall finally did switch parties in 2004, after the Republicans refused to put money for his district in a spending bill. When he asked why, he said "the only reason I was given was that I was a Democrat." Hall also cited concerns with the Democrats' criticism of President Bush; he had not attended Democratic caucus meetings for some time as a result. He was allowed to keep his seniority, and became chairman of the House Energy Subcommittee on Energy and Air Quality. Later that year, he ran for his first full term as a Republican and won with 68 percent of the vote.

Some had thought that he would replace Sherwood Boehlert of New York as chairman of the House Science Committee. Boehlert is a leading moderate Republican favored by environmental interests, while Hall has strong ties to the oil and gas industry. However, this did not happen either after his party switch or the 2004 elections.

Hall is only the fourth person to represent the 4th District since its creation in 1903. The district's second congressman, longtime Speaker Sam Rayburn, had represented the district for 48 years. Hall's predecessor, Ray Roberts (for whom Lake Ray Roberts in Texas is named), had served for 19 years.