When Secretary of State Alexander Haig attempted to calm the nation’s fears after the assassination attempt on President Ronald Reagan, it was one of those moments that made history. Unfortunately, it was the kind of history no one wants to be remembered for.

With the president in emergency surgery and Vice President George H.W. Bush on board Air Force Two and still hours away from Washington, DC, Haig rushed to the White House Press Room to speak to reporters. “Constitutionally, gentlemen, you have the president, the vice president, and the secretary of state, in that order. And should the president decide he wants to transfer the helm to the vice president, he will do so. As of now, I am in control here at the White House, pending the return of the vice president.”

Although Haig would later insist that he was referring solely to the conduct of operations at the White House, the fact that he invoked the Constitution suggested otherwise. He seemed to think he was next in line to the presidency after the vice president. In reality, two other men stood in line before the reins of government could fall into his hands. This, of course, overlooks the fact that under the terms of the Constitution, all executive authority still rested with President Reagan and would remain so unless he voluntarily relinquished it or the vice president invoked the provisions of the 24th amendment (see this post about what happens if the president is incapacitated or insane).

In Haig’s defense, his understanding of the order of presidential succession is likely what he was taught when he was a teenager in school. Congress has the authority to designate the line of succession following the vice president, and it has changed its mind a couple of times in the past two centuries.

The first time Congress addressed this issue was with the Presidential Succession Act of 1792. It stated that if there was no president or vice president, the office would go to the president pro tempore of the Senate. The speaker of the House of Representatives was next in line.

A curious provision of the 1792 Act was that if both the president and vice president were dead or otherwise unable to serve, the individual next in line would hold the office only until a new president could be elected. The special election was required to be held within two months. The individuals elected as president and vice president at that special election would take office on the next March 4, and they would serve a four-year term commencing on that date.

By way of example, President Zachary Taylor was elected in November 1848 and took office on March 4, 1849. He died on July 9, 1850. Fortunately, Vice President Millard Fillmore was able to assume the presidency, and he finished out Taylor’s term. The next presidential election was in November 1852 — four years after the prior one. If Fillmore had not been able to take office upon Taylor’s death, things would have worked differently. The 1792 Act would have given the presidency to the president pro tempore of the Senate, William Rufus King. (Read this article and learn how King was the one man who was next in line to the presidency on two separate occasions). King would not have finished out Taylor’s term, however. A new president would have to be elected within two months. The president-elect would remain waiting in the wings until March 4, 1851. On that day, King would turn over the office to the president-elect, who would then commence a four-year term. This would mean that all subsequent presidential elections would take place three years later than originally scheduled.

Several problematic issues about the 1792 Act needed to be addressed, but it would take nearly a century before Congress got around to dealing with them. One murky issue surrounded the process for electing the Senate’s president pro tempore. For most of the 19th century, the Senate operated as if it could elect a president pro tempore only during the absence of a vice president. Congress tended to be out of session for half of each year. In an era of high mortality rates, this could be a serious problem if both the president and vice president died while Congress was not in session and there was no president pro tempore. In an effort to avoid this scenario, the Senate acted out an elaborate charade in which the vice president would voluntarily leave the chamber before the end of a session, thus allowing the Senate to elect a president pro tempore. On occasion, however, this plan failed. Occasionally a vice president would refuse to leave the chamber when the opposition party held the majority to prevent the possibility of the presidency passing into the hands of the other political party.

After 94 years of this system for ensuring the continuity of government, Congress adopted the Succession Act of 1886. The new and improved process for presidential succession removed the speaker and president pro tempore, replacing them with the members of the cabinet in the order of their agencies’ creation. Those who favored this change pointed out that the qualifications for serving as president are substantially different from those of leading a parliamentary body. No president pro tempore had ever served as president, but six former secretaries of state had been elected to the office. Additionally, since cabinet members tend to be members of the same political party as the president, this would avoid the spectacle of the White House being taken over by a party that had not been elected to the presidency.

It was the Act of 1886 that was in effect when Alexander Haig was in grade school. Undoubtedly, he was taught that the secretary of state is next in line after the vice president. One might excuse him for not knowing that all of that changed in 1947. It was that year that Congress once again switched things around.

Franklin D. Roosevelt’s death in 1945 brought Harry S. Truman to the presidency. Truman believed that the chief executive should be someone who was an elected representative of the people, rather than an appointed government department head. At his urging, Congress adopted the Succession Act of 1947. It again placed the top individuals in the House and the Senate next in line after the vice president. Unlike the Act of 1792, however, the new order gave the speaker of the House priority over the president pro tempore of the Senate. Some have speculated that this may have had something to do with Truman’s strained relationship with 78-year-old President Pro Tempore Kenneth McKellar and his close friendship with 65-year-old Speaker Sam Rayburn.

The Act of 1947 retained the members of the cabinet in the line of succession, beginning with the secretary of state, who is next in line after the president pro tempore. The Act of 1947 remains in effect to this day, but it has been amended from time to time when cabinet offices have been renamed, removed, or added. It was last revised in 2006 when the Secretary of Homeland Security became a cabinet-level position. Additionally, the 25th Amendment was adopted in 1967 and provides procedures for filling an intra-term vacancy in the office of the vice president.

Fortunately, the line of succession beyond the vice presidency has been academic thus far. Since 1789, the vice president has succeeded to the presidency because of the death or resignation of the president on nine occasions. No one lower in the line of succession has ever been called upon to act as president.

There have, however, been some close calls where the continuity of government hung by a spiderweb:

• July 9, 1850 – July 11, 1850 — Following the death of Zachary Taylor, Millard Fillmore became president. This left a vacancy in the vice presidency. The senate had not elected a president pro tempore, and Speaker Howell Cobb was two months shy of his 35th birthday, making him too young to be president.
• September 19, 1881 – October 10, 1881 — Chester A. Arthur became president upon the death of James Garfield. This left a vacancy in the vice presidency. At the same time, there was no speaker of the House or president pro tempore.
• November 25, 1885 – December 7, 1885 — Grover Cleveland’s vice president, Thomas A. Hendricks, died in office. There was a vacancy in the office of president pro tempore and the office of speaker of the House.

Keeping track of who is next in line and where that person can be found is of great importance in the Nuclear Age. The Central Locator System was a program of the U.S. Federal Emergency Management Agency (FEMA) that kept around-the-clock status on the location of those in the line of succession.

A copy of the Communications Handbook for Central Locator System from 1973 is available by clicking on the link. Since declassified, it was provided to Senator James O. Eastland who, as president pro tempore of the Senate, was next in line of succession after the vice president and the speaker of the House. The Handbook describes the procedure for keeping track of those who are in the line of succession. Essentially, it required regular updates to the White House Communications Agency whenever a presidential successor leaves the Washington, DC metropolitan area. In times of emergency, regular updates about the individual’s location within Washington, DC was required, as well.

The Handbook also included instructions about how to get through to the White House Communications Agency if the phone system is overwhelmed. It instructs the person to call his local operator for assistance and state: “This is a FLASH EMERGENCY call.” (Details about the FLASH OVERRIDE telephone system can be found in this article).

Since then, the Central Locator System has been replaced by the Internet Protocol Locator. The details of how this operates are classified, but it can be safely assumed that none of the 20 presidential successors have the luxury of sneaking off without someone knowing about it.