What ever happened to Congress? In recent weeks, the United States has seen an undeclared war in the Caribbean, military deployments to American cities, a government shutdown, and President Trump’s solo takeover of the power to lay tariffs—all actions that Congress would have needed to approve. Instead, the federal government has shut down. The House of Representatives is actually closed.

For much of the nation’s history, the legislature functioned as the preeminent branch of the federal government. Even during the 20th century, when both the courts and the presidency gained power and stature, Congress jealously guarded its prerogatives. Sure, senators and representatives had partisan loyalties and ideological commitments that often encouraged deference to the executive branch (especially when controlled by a president of the same party affiliation). But members of Congress remained committed to preserving the power of their own institution. What happened?

To be sure, the shift of power away from Congress and towards the presidency proceeded gradually over a century. Two developments of the 1970s and 1980s—the internal restructuring of Congressional operations and the ideological sorting of the parties—punctured a long tradition of institutional independence. The unwillingness and inability of the legislative branch to check the executive stems largely from those well-intentioned reforms.

The U.S. Constitution makes clear the intended predominance of the legislative branch. The document’s first section, Article I, laid out the contours of the Congress and assigned it the most important political powers: to make laws, collect taxes, declare war, coin money, conclude treaties, and oversee elections. Significantly, Congress could remove presidents and judges through its impeachment power. The other branches cannot remove legislators.

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Throughout the 19th century, while presidents sometimes exercised their legislative veto and claimed emergency powers, Congress remained the main policymaking institution—the seat of federal authority. Analyzing the structure and function of American government in 1885, a young professor named Woodrow Wilson called Congress “the dominant, nay the irresistible, power of the federal system”; the president, he concluded, was “plainly bound in duty to render unquestioning obedience to Congress.” Indeed, just a few years earlier, President James Garfield had concurred, dismissing the presidency as “a bleak mountain” as he wondered, “What is there in this place that a man should ever want to get into it?”

Over the course of the 20th century, the balance of power shifted toward the executive. In part, that reflected the efforts of some presidents to expand their authority. Advancing the “stewardship” theory, Theodore Roosevelt asserted that the president’s status as the only nationally elected officeholder meant he could pursue the national interest in any way he saw fit, so long as the law did not explicitly forbid it. On his authority, Roosevelt added millions of acres to the national forest preserves. Incensed, Congress, including members of his own party, passed a law prohibiting the president from setting aside further lands. They attached it to an appropriations bill that Roosevelt could not veto. He signed it, but in the days before doing so, Roosevelt proclaimed 21 new forest preserves and added territory to 11 existing ones. The so-called midnight forests totaled more than 16,000,000 acres of new reserves—pretty much all of the potentially reservable land in those states.

Over the next half century, the demands of modern crises, like economic depression and global war, further rebalanced power between the branches of government. In the post-World War II era, Congress more and more acknowledged these new realities by delegating specific authority to the executive branch. The 1946 Full Employment Act and the 1947 National Security Act essentially made the president responsible for, and provided him new tools to oversee, economic performance and national security. That trend deepened in the 1960s, when Congress pretty much granted President Lyndon Johnson carte blanche in Vietnam. The 1977 law under which Trump claims his tariff powers is another example of that power shifting.

And yet, Congress still maintained oversight of those executive actions and set rules (currently challenged by Trump) on how the president can appoint and fire officials. At some points, the legislative branch even tried to claw back authority. For example, amid post-Watergate concerns about the “imperial presidency,” it rammed through the War Powers Act (overriding the president’s veto), set up new procedures for investigating the executive branch, and limited the president’s power to impound congressionally-appropriated funds. (President Trump, his critics charge, has defied both the Impoundment Act and the War Powers Act.)

At that very historical moment, however, during the 1970s and early 1980s, reforms on Capitol Hill—designed to promote transparency and empower junior members—paved the way for Congress’ current impotence. Up through the 1960s, the House and Senate remained rigidly hierarchical bodies: powerful leaders, especially a coterie of long-serving committee chairman, set the legislative agenda and disciplined junior members through their control of committee assignments, resources, and access to favorable publicity. Commentators referred to Congress as a set of feudal manors and its leaders as “barons.” William S. White, who covered the Senate for the New York Times called its chairmen “emperors.”

To be sure, those “barons” cared about the needs of their home states; sometimes, they also advanced the interests of their party or their ideological agenda. But their power stemmed from (and reinforced) a fierce defense of Congress as an institution. Their influence rose and fell with the authority of the legislative branch.

Frustrated by the barons’ stranglehold over the legislative process, a younger generation of legislators, energized by the large number of “Watergate babies,” who arrived after the 1974 elections, pushed through a series of rules changes. By the early 1980s, they had stripped committee chairs of much of their power, weakened the seniority system, distributed resources more evenly among members, and opened the legislative process to greater public scrutiny. For example, in 1971 the House restricted members to one subcommittee chairmanship, distributing those positions and their staff more evenly.

The reforms effectively transformed the Congress from a set of tightly managed fiefdoms into an everyone-for-themselves collection of free agents. The Senate has largely remained that way. The larger, more unwieldy House eventually adjusted to reforms by investing more power in the leadership of the majority party (speakers and their lieutenants), but they were party leaders invested in a partisan agenda, rather than reservoirs of institutional autonomy.

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The second key development—ideological sorting of the parties—reinforced those internal changes. Through the 1970s, the two major parties remained diverse coalitions; the Republican Party contained prominent liberals and the Democrats many conservatives. Both parties competed in just about every area of the country. Party caucuses differed broadly and fundamentally on most issues. That affected legislation: for example, a Democratic President, even with a Democratic congressional majority, needed Republican votes to pass the Civil Rights Act. But it also meant that protecting the power and independence of the Congress competed with and sometimes trumped partisan loyalties. The 1974 Impoundment Act prohibiting presidents from messing with spending mandated by Congress (the law current that OMB Director Russell Vought denounces as unconstitutional) passed unanimously in the Senate and by 401-6 in the House.

As the parties became ideologically distinct with the disappearance of the last liberal Republicans and conservative Democrats, such bipartisan assertions of congressional prerogative have faded. Partisan sorting in Congress has also stymied action on Capitol Hill, which has in part led to five federal government shutdowns since 1980.

During Trump’s first term, Senator John McCain (R-Ariz.) famously cast the deciding no vote against Obamacare repeal, not to preserve a law that he opposed, but to defend “regular order” in the Senate. By that time, such appeals already seemed quaint.

Still, in today’s era of unchecked executive power, Americans could do well to remember McCain’s plea that Congress “discharge its constitutional responsibilities.”

*Bruce J. Schulman is the William Huntington professor of history at Boston University and author of *The Seventies: The Great Shift in American Culture, Politics, and Society.

Made by History takes readers beyond the headlines with articles written and edited by professional historians. Learn more about Made by History at TIME here. Opinions expressed do not necessarily reflect the views of TIME editors.