In June 1855, the people of Lawrence had a meeting and decided to resist any laws the Kansas legislature passed. They believed the legislature was elected by armed Missouri people, not Kansas people. Amos Lawrence and others sent crates full of rifles. They wrote on the crates that the things inside were books because "the border ruffians had no use for books," so they did not take the rifles when they came to Lawrence. Horace Greeley helped send a howitzer to Lawrence.
On November 21, 1855, the pro-slavery man Franklin N. Coleman shot anti-slavery man Charles Dow in the head. This killed him. This happened after many angry arguments between them about land claims. When Sheriff Samuel Jones investigated the crime, Franklin Coleman said he shot Charles Dow in self-defense. Jones believed Coleman because they both were pro-slavery men. Jones decided to arrest Jacob Branson, a friend of Charles Dow and an anti-slavery man, for disturbing the peace. A group of anti-slavery people saved Branson.
Wilson Shannon, the governor of the Kansas Territory, saw that the people were becoming very angry and violent. He asked the Kansas militia to come and keep the peace. Shannon wanted the people in the militia to be from Kansas, but Samuel Jones brought 1,200-1,500 men from Missouri. When the people of Lawrence learned this, they made a militia of 600-800 men. They chose Robinson to lead the militia. James H. Lane was chosen as his second-in-command. John Brown and his four sons also joined to fight. Both groups were ready to fight, but they could not because the winter was very cold. Wilson Shannon decided to prevent a fight. He demanded that the leaders of both sides agree to a peace treaty. They did, and the men from Missouri went back to Missouri. This "war" is known as the Wakarusa War.
In spring 1856, pro-slavery people wanted to make the free-staters weak. The pro-slavery people said that the "Herald of Freedom" newspaper, the "Kansas Free State" newspaper, and the Eldridge Hotel were very bad. On April 23, 1856, Samuel Jones came to Lawrence. He tried to arrest some anti-slavery people who had created their own anti-slavery government. A sniper shot Samuel Jones, but he did not die. The people of Lawrence made Jones leave. On May 11, Federal Marshall (like a police officer but for the entire country) Israel B. Donaldson said that people interfered with Samuel Jones which was not legal. A Kansas grand jury agreed. They said that Lawrence built the Free State Hotel (the Eldridge Hotel) for military purposes. Donaldson, Jones, and others recruited an army of 800 men to enforce the law. However, they also wanted to stop the anti-slavery men in Lawrence.
On May 21, Donaldson and Jones took their army to Lawrence. They arrested more anti-slavery people. The people of Lawrence hoped that Donaldson and Jones would leave after the arrests, but this did not happen. Jones and his men started sacking Lawrence. They took over Charles Robinson's house and used it as a headquarters. They attacked free-state newspapers offices. They struck the printing presses, and they threw the sort into the Kansas River. They shot the Free State Hotel (the Eldridge Hotel) using a cannon and burned it down. They took $30,000 worth of things. After burning Charles Robinson's house, the army left. The day of destruction was called the "Sacking of Lawrence." Surprisingly, only one person died; a man died when he was hit by falling masonry. In late September 1856, another sack seemed like it was about to happen when 2,700 pro-slavery men came to Lawrence. Anti-slavery men defended the city. Governor John W. Geary saw what was happening. He asked for federal reinforcements to defend the city. No violence happened.
In 1855 and 1857, Lawrence got a charter (a document that officially creates a town) from the pro-slavery Kansas government. The people of Lawrence resisted the Kansas government because they believed they were too pro-slavery. They did not accept it because it would force Lawrence to follow pro-slavery laws. In July 1857, the people of Lawrence tried to get an "official" (only the people of Lawrence saw it as official) charter from the extralegal (having no real authority) anti-slavery government. If they could not get one, Lawrence would simply make one themselves. Governor Robert J. Walker believed this was a revolt. On July 15, 1857, he sent an army to Lawrence and declared martial law. The army stayed close to Lawrence until October 1857. They stayed until October because there were elections. They wanted to make sure that there would be no violence at the elections. Anti-slavery people won the elections. The Kansas government became controlled by anti-slavery people. In early 1858, Samuel Jones quit his job, and he left Kansas. On January 16, 1858, Lawrence became the county seat of Douglas County. In February 1858, the Kansas government approved an anti-slavery charter for Lawrence. James Blood became the first mayor of Lawrence. The anti-slavery Kansas government met in Lawrence many times. In practice, Lawrence became the capital of Kansas from 1858 until 1861.
On October 4, 1859, the people of Kansas voted to approve the Wyandotte Constitution. There were 10,421 "yes" votes and 5,530 "no" votes. The United States Congress approved the Wyandotte Constitution. Kansas became a free state on January 29, 1861. Pro-slavery people in Kansas knew they had lost. Kansas becoming a free state ended Bleeding Kansas. However, the American Civil War began around the same time.
During the war, many Jayhawkers stayed in Lawrence. These Jayhawkers went to Missouri. They stole items and burned farms there. Many people in the Confederacy believed that the stolen items were in Lawrence. On August 21, 1863, a pro-slavery man named William Quantrill rode into Lawrence with some men. They destroyed much of the town. They killed every adult man they saw. More than 150 men and boys died. There was 2,000,000 dollars worth of property destroyed. The Plymouth Congregational Church was not destroyed, but many of its people died. This attack is known as the Lawrence massacre.
After Quantrill's Raid, the people and Union soldiers rebuilt the city. It was not easy because the winter was very cold. They continued rebuilding until they finished in 1864. While they were rebuilding, the people of Lawrence were afraid of another attack. The military built some camps in Lawrence to guard the city, but no more attacks happened. After the Civil War, the camps were closed and removed.
There was a plan to build a university in Kansas in 1855, but it did not happen until Kansas became a state in 1861. The Kansas government needed to decide where to build the university. Their choices were Manhattan, Emporia, or Lawrence. On January 13, 1863, Kansas State University was built in Manhattan. However, the Kansas government decided to build another one. The only cities left where a university could be built were Emporia and Lawrence. Amos A. Lawrence gave $10,000 and more than 40 acres (160,000 m) of land for a university in Lawrence. The Kansas government liked that, so the government chose Lawrence. The University of Kansas opened in 1866.
In 1864, Lawrence got its first railroad. It connected Lawrence to Kansas City. The first train to go to Lawrence went on November 28, 1864. The first train to cross the Kansas River crossed it in Lawrence on November 1, 1867.
In the early 1870s, Lawrence needed more electricity. The city asked Orlando Darling to build a dam on the Kansas River. Darling became angry because it took a long time to build a dam, so he stopped. The Lawrence Land & Water Company finished building the dam in 1873. The dam made Lawrence special because few cities had a dam. The dam closed in 1968, but the city reopened it in 1977. They wanted to build a new city hall next to the dam. Today, the dam helps prevent flooding.