of American politics,

they often mention the dominance of

the Democratic and Republican Parties,

or the sharp split between red and blue states.

But while it may seem like both of these things

have been around forever,

the situation looked quite different in 1850,

with the Republican Party not yet existing,

and support for the dominant Democrats and Whigs

cutting across geographic divides.

The collapse of this Second Party System

was at the center of increasing regional tensions

that would lead to the birth of the Republican Party,

the rise of Abraham Lincoln as its leader,

and a civil war that would claim over half a million lives.

And if this collapse could be blamed

on a single event,

it would be the Kansas-Nebraska Act of 1854.

The story starts with the Missouri Compromise of 1820.

To balance the number of slave states

and free states in the Union,

it allowed slavery in the newly admitted

state of Missouri, while making it off limits

in the remaining federally administered Louisiana Territory.

But compromises tend to last

only as long as they're convenient,

and by the early 1850s,

a tenacious Democratic Senator from Illionis

named Stephen A. Douglas

found its terms very inconvenient.

As an advocate of western expansion,

he promoted constructing a transcontinental

railroad across the Northern Plains

with an eastern terminus in Chicago,

where he happened to own real estate.

For his proposal to succeed,

Douglas felt that the territories

through which the railroad passed,

would have to be formally organized,

which required the support of Southern politicians.

He was also a believer in popular sovereignty,

arguing that the status of slavery in a territory

should be decided by its residents rather than Congress.

So Douglas introduced a bill

designed to kill two birds with one stone.

It would divide the large chunk of incorporated land

into two new organized territories: Nebraska and Kansas,

each of which would be open to slavery

if the population voted to allow it.

While Douglas and his Southern supporters

tried to frame the bill as protecting

the political rights of settlers,

horrified Northerners recognized it as

repealing the 34-year-old Missouri Compromise

and feared that its supporters' ultimate goal

was to extend slavery to the entire nation.

Congress was able to pass the Kansas-Nebraska Act,

but at the huge cost of bitterly dividing the nation,

with 91% of the opposition coming from Northerners.

In the House of Representatives,

politicians traded insults and brandished weapons

until a Sargent at Arms restored order.

President Pierce signed the bill into law

amidst a storm of protest,

while Georgia's Alexander Stephens,

future Confederate Vice President,

hailed the Act's passage as,

"Glory enough for one day."

The New York Tribune reported,

"The unanimous sentiment of the North is indignant resistance."

Douglas even admitted that he could travel

from Washington D.C. to Chicago

by the light of his own burning effigies.

The political consequences

of the Kansas-Nebraska Act were stunning.

Previously, both Whigs and Democrats had included

Northern and Southern lawmakers united around

various issues, but now slavery became

a dividing factor that could not be ignored.

Congressmen from both parties

spoke out against the act,

including an Illinois Whig named Abraham Lincoln,

denouncing "the monstrous injustice of slavery"

in an 1854 speech.

By this time the Whigs had all but ceased to exist,

irreparably split between

their Northern and Southern factions.

In the same year, the new Republican Party

was founded by the anti-slavery elements

from both existing parties.

Although Lincoln still ran for Senate as a Whig in 1854,

he was an early supporter of the new party,

and helped to recruit others to its cause.

Meanwhile the Democratic Party was shaken

when events in the newly formed Kansas Territory

revealed the violent consequences of popular sovereignty.

Advertisements appeared across the North

imploring people to emigrate to Kansas

to stem the advance of slavery.

The South answered with Border Ruffians,

pro-slavery Missourians who crossed state lines

to vote in fraudulent elections

and raid anti-slavery settlements.

One northern abolitionist, John Brown,

became notorious following the

Pottawatomie Massacre of 1856

when he and his sons hacked to death

five pro-slavery farmers with broad swords.

In the end, more than 50 people

died in Bleeding Kansas.

While nominally still a national party,

Douglas's Democrats were increasingly divided

along sectional lines,

and many Northern members left

to join the Republicans.

Abraham Lincoln finally took up

the Republican Party banner in 1856

and never looked back.

That year, John C. Fremont,

the first Republican presidential candidate,

lost to Democrat, James Buchanan,

but garnered 33% of the popular vote

all from Northern states.

Two years later, Lincoln challenged Douglas

for his Illinois Senate seat,

and although he lost that contest,

it elevated his status among Republicans.

Lincoln would finally be vindicated in 1860,

when he was elected President of the United States,

defeating in his own home state,

a certain Northern Democrat,

who was finally undone by the disastrous

aftermath of the law he had masterminded.

Americans today continue to debate

whether the Civil War was inevitable,

but there is no doubt that the

Kansas-Nebraska Act made the ghastly conflict

much more likely.

And for that reason,

it should be remembered as one of the most

consequential pieces of legislation

in American history.