Alvin Jacob Wirtz, lawyer, legislator, organizer of the Lower Colorado River Authority, and undersecretary of the Department of the Interior, was born in Columbus, Texas, to Lewis Milton and Dora (Dent) Wirtz on May 24, 1888. Wirtz attended Columbus public schools and graduated from the University of Texas with a LL.B degree in 1910. He was admitted to the bar that year and practiced law at Columbus and Eagle Lake in Colorado County from 1910 to 1917. Wirtz married Kitty Mae Stamps of Seguin on November 18, 1913; they had one daughter. In 1917 Wirtz moved his family to Seguin, where he continued his law practice until 1934. From 1922 to 1930 he served as state senator from Guadalupe County. During his time in the legislature, Wirtz became involved with a group of citizens interested in the development of the Guadalupe River as a source of hydroelectric power. Emery, Peck, and Rockwood, a subsidiary of Samuel Insull's industrial holdings, built a chain of privately owned dams and hydroelectric projects on the Guadalupe and later began construction of Hamilton Dam on the Colorado River. When the stock market crash of 1929 toppled the Insull empire, Wirtz was appointed receiver, on behalf of Texas creditors, of the state's Insull properties, including the unfinished dam project. He then promoted the formation of the Lower Colorado River Authority. In the Texas Senate he wrote the legislation that in 1934 established the authority as a state agency. In 1934 Wirtz moved to Austin, reportedly run out of Seguin by disgruntled farmers who believed his dam projects had cheated them out of their land. In Austin he organized the law firm of Powell, Wirtz, Rauhut, and Gideon. He specialized in oil and water law and was appointed general counsel to the newly established LCRA. Working closely with United States Representative Lyndon Baines Johnson, he helped the river authority secure grants and loans from the Public Works Administration, the Reconstruction Finance Corporation, and the Rural Electrification Administration. He also aided in the formation of rural electric cooperatives in counties throughout central Texas. Although irrigation, flood control, and inexpensive hydroelectric power in the rural counties resulted from the river developments, the projects were completed only after a long and spirited struggle against the private utility companies. Wirtz's leadership and legal expertise throughout the public power fight were instrumental in the project's fulfillment.
As an early supporter of the political career of Lyndon B. Johnson, Wirtz helped the young congressman obtain numerous federal projects for the Tenth Congressional District, enlisted powerful supporters for Johnson's early campaigns, and aided the future president's United States Senate races in 1941 and 1948. In 1948 he represented the candidate before the canvassing subcommittee of the Democratic State Executive Committee and led the successful fight in which Johnson was declared winner (by eighty-seven votes) over Coke R. Stevenson in a contested election. An influential figure in Democratic politics, Wirtz was a delegate to the 1928, 1932, and 1940 Democratic national conventions. He actively promoted Franklin D. Roosevelt's renomination bids in 1940 and 1944. He served as chairman of the National Youth Administration's advisory board for Texas and as director of the Austin housing authority. In January 1940 President Roosevelt appointed Wirtz undersecretary of the Department of the Interior, a position he resigned in May 1941 to return to his Austin law firm and to aid Johnson's U. S. Senate campaign against W. Lee O'Daniel. During World War II Wirtz acted as negotiator for the president's cabinet committee for Saudi Arabian oil. In 1943 Secretary of the Interior Harold L. Ickes named Wirtz as a consultant on power affairs.
Wirtz was also an expert in oil and gas law, and he represented such prominent clients as Brown and Root Company of Houston and independent petroleum producer Sid Williams Richardson. Early in his career, he gained a reputation as a staunch advocate of civil liberties, and in 1939 he successfully led the defense of F. Maury Maverick during an indictment regarding campaign practices in San Antonio. Wirtz was a member of the American and Texas state bar associations; he was an Elk, a Thirty-second degree Mason, and a member of the Baptist church. He died in Austin of a heart attack on October 27, 1951, and was buried in the State Cemetery. The Granite Shoals Dam, four miles west of Marble Falls on the Colorado River, was renamed the Alvin Wirtz Dam in December 1951.