In 1901, Carnegie was 66 years of age and considering retirement. He reformed his enterprises into conventional joint stock corporations as preparation for this. John Pierpont Morgan was a banker and America's most important financial deal maker. He had observed how efficiently Carnegie produced profits. He envisioned an integrated steel industry that would cut costs, lower prices to consumers, produce in greater quantities and raise wages to workers. To this end, he needed to buy out Carnegie and several other major producers and integrate them into one company, thereby eliminating duplication and waste. He concluded negotiations on March 2, 1901, and formed the United States Steel Corporation. It was the first corporation in the world with a market capitalization over $1 billion.
Carnegie's share of this amounted to $225.64 million (in 2019, $6.93 billion), which was paid to Carnegie in the form of 5%, 50-year gold bonds. The letter agreeing to sell his share was signed on February 26, 1901. On March 2, the circular formally filing the organization and capitalization (at $1.4 billion – 4 percent of the U.S. gross domestic product (GDP) at the time) of the United States Steel Corporation actually completed the contract. The bonds were to be delivered within two weeks to the Hudson Trust Company of Hoboken, New Jersey, in trust to Robert A. Franks, Carnegie's business secretary. There, a special vault was built to house the physical bulk of nearly $230 million worth of bonds.
In 1901, in Scotland, he gave $10 million to establish the Carnegie Trust for the Universities of Scotland. It was created by a deed which he signed on June 7, 1901, and it was incorporated by Royal Charter on August 21, 1902. The establishing gift of $10 million was then an unprecedented sum: at the time, total government assistance to all four Scottish universities was about £50,000 a year. The aim of the Trust was to improve and extend the opportunities for scientific research in the Scottish universities and to enable the deserving and qualified youth of Scotland to attend a university. He was subsequently elected Lord Rector of University of St. Andrews in December 1901, and formally installed as such in October 1902, serving until 1907. He also donated large sums of money to Dunfermline, the place of his birth. In addition to a library, Carnegie also bought the private estate which became Pittencrieff Park and opened it to all members of the public, establishing the Carnegie Dunfermline Trust to benefit the people of Dunfermline. A statue of him stands there today.
In 1901, Carnegie also established large pension funds for his former employees at Homestead and, in 1905, for American college professors. The latter fund evolved into TIAA-CREF. One critical requirement was that church-related schools had to sever their religious connections to get his money.
After he sold his steel company in 1901, Carnegie was able to get fully involved in the peace cause, both financially and personally. He gave away much of his fortunes to various peace-keeping agencies in order to keep them growing. When his friend, the British writer William T. Stead, asked him to create a new organization for the goal of a peace and arbitration society, his reply was:
Carnegie received the honorary Doctor of Laws (DLL) from the University of Glasgow in June 1901, and received the Freedom of the City of Glasgow "in recognition of his munificence" later the same year. In July 1902 he received the Freedom of the city of St Andrews, "in testimony of his great zeal for the welfare of his fellow-men on both sides of the Atlantic", and in October 1902 the Freedom of the City of Perth "in testimony of his high personal worth and beneficial influence, and in recognition of widespread benefactions bestowed on this and other lands, and especially in gratitude for the endowment granted by him for the promotion of University education in Scotland" and the Freedom of the City of Dundee. He received an honorary Doctor of Laws (LLD) from the University of Aberdeen in 1906. In 1910, he received the Freedom of the City of Belfast. Carnegie received 1 July 1914 an honorary doctorate from the University of Groningen the Netherlands.