Who votes? How are they represented? What should be the scope and scale of government? Who pays taxes and how do they affect the distribution of wealth and power? These four questions will drive the long march to the 2020 election as the nation grapples with new voter suppression laws, redistricting campaigns and, for Democrats, the platforms of over two dozen presidential contenders who promise to combat economic inequality, meet the challenges of mass immigration and reduce the insidious influence of big money in American politics.

But these are not simply questions for the 21st century. They also comprise some of the most fundamental — and enduring questions — in the history of American democracy. In fact, over a century ago, as the country wrestled with similar questions, a dramatic series of constitutional and legal innovations between 1911 and 1920 transformed the structure and content of American public life. Together they redrew the playing field of American politics. And to a large extent, Americans are still playing by those rules.

The stunning decade of constitutional change began with the admission of two new states, New Mexico and Arizona. When they joined the union as the 47th and 48th states, they sent the 434th and 435th members to the House of Representatives and launched a still-ongoing debate about reapportioning congressional representation among the states and drawing congressional district lines within them. Although disputes over gerrymandering may trace back to the early Republic, the federal Congress had added members nearly every decade for a century so that reapportionment always involved the allocation of more seats, rather than a redistribution of them and states losing House members. After 1912, however, it became a zero-sum game with Congress refusing to add seats after the 1920 census and formally capping the number of House members at 435 in 1929.

The precedent-defying refusal to add seats in 1920 especially mattered because between 1910 and 1920, the urban population had grown by 19 million people while rural areas actually shrank by 5 million.

To keep with its practice of adding seats and preventing states from losing congressional seats after 1920, however, Congress would have had to add an unwieldy 50 new members. But if the House remained at 435, a dozen states would lose seats and power would swing from the South and Midwest to the urban Northeast. Since that threatened both the Republican majority and the power of southern Democrats, the GOP and a handful of the southerners stonewalled for a decade before finally conceding, and allowing the House to be capped at 435 seats.

With three times as many Americans today as in 1911, that decision creates huge districts of widely varying size. Representatives have therefore become more reliant on lobbyists and large contributors, less responsive to constituents and inimical to the democratic principle of one person, one vote.

In 1913, a year after admitting New Mexico and Arizona, the states ratified both the 16th and 17th amendments. The latter had an immediate impact, providing for the direct election of senators rather than selection by state legislatures — an effort both to combat political machine power over the electoral process and to prevent long vacancies caused when different parties controlled the two houses of a state legislature. The amendment cured the vacancy problem and ended the practice of bribing state legislators to gain their support for Senate, but it failed to fulfill reformers’ hopes that the Senate would become less of a “millionaire’s club” susceptible to the influence of special interests.

The former — the income tax amendment — did not have such an obvious immediate impact because initially so few Americans would be subject to the tax, and even fewer subject to state income taxes. But in the long term, it transformed the fiscal basis of American governance from regressive taxes on goods to progressive levies on income and wealth. Almost overnight, this amendment transformed the source of revenue for federal government. In 1910, customs duties accounted for nearly half of all federal government receipts, with alcohol and tobacco taxes making up another 39 percent. A decade later, the income tax furnished the majority of federal revenue.

This fiscal revolution facilitated fundamental changes in the size, scope and purposes of government. It allowed for the funding of a wide range of public goods and services and regulatory agencies to oversee them. It also required the development of an administrative capacity to track income, profits and inheritances, which meant gathering a lot more information about people’s economic lives. In short, it underwrote the subsequent expansion of the modern American state.