How does Huck take initiative in becoming mature throughout the book? (with quotes)

During his adventures on land and the Mississippi River, Huckleberry Finn takes the initiative in certain matters that point to his maturation.
The first thing that Huck does which points to a growing maturity is to contact Judge Thatcher as soon as he detects that his derelict father is around. Huck worries that Pap will take his share of the stolen fortune that he and Tom Sawyer had discovered and were allowed to keep. The boys entrusted this money to the judge, who paid out interest at a dollar a day to each of them. However, when Huck sees the distinguishing mark of Pap's boot heel, he fears that Pap will take the money from him. So Huck contacts Judge Thatcher and tries to give him his share, but the judge has him sign a paper that reads "for a consideration"; by this wording, Judge Thatcher means that he has purchased the money from Huck. Since the judge is an honorable man, Huck does not need to worry about retrieving it. In the judge's hands, the money is safe from anyone else.
After a judge who does not know Huck's father allows Pap to remain Huck's legal guardian, Pap chases Huck with a knife and locks him away in a cabin for hours. But, one day when his father is gone, knowing that he must escape his father's abuse, Huck saws a hole in an outer wall and crawls out. Huck spreads some pig's blood around the cabin and, after pulling out some of his hair, he lays the blood and hair around to create what appears to be a struggle. Then, he takes the canoe that he found washed ashore and departs. Not long after this, Huck runs into Miss Watson's Jim, who has escaped.
As Jim and Huck travel down the Mississippi River together, several incidents occur. One of these is cause for Huck to examine his conscience and consider the feelings of others. When they are only two or three days from Cairo, Illinois, at the very bottom of the state, they come to where the Mississippi River meets the Ohio River, on which Jim hopes to travel and earn freedom in the North. Unfortunately, there is a thick fog that comes in. Huck tries to tie the raft to a branch, but the rapid current pulls the raft loose and Jim along with it. Some distance away, Huck hears Jim, but he cannot find him with the canoe because of the fog, which impairs his senses. Consequently, Huck and Jim are separated for hours. After the fog clears, Huck locates the raft where Jim is fast asleep. The mischievous boy decides to trick Jim when he awakens and is overjoyed to see the boy. Huck declares that he has been on the raft all the time; he convinces Jim that he merely dreamed that they were separated in a fog. Finally, Huck tells Jim the truth, causing Jim to glare at Huck in his hurt and anger. He tells Huck that when he thought Huck was lost, his heart "wuz most broke. Jim scolds Huck; then he retreats into the wigwam on the raft without speaking. Huck sits there, pondering how he has hurt Jim, who apparently loves him. Surprised by Jim's deep emotions, it is at this point that Huck begins to perceive Jim as a man, rather than as a slave or property.

It made me feel so mean I could almost kissed his foot to get him to take it back. It was fifteen minutes before I could work myself up to go and humble myself to a n****r--but I done it, and I warn't ever sorry for it afterwards, neither." (Ch.14)

Further, Huck states that if he had known that Jim would worry so much and be so hurt, he would not have played this trick on him, words that also indicate a growing maturity.
Later on, Huck tells some men who approach them that there is smallpox on their raft. He says this so that the men will not come close enough to notice that Jim is black. When a steamboat strikes them, Huck makes it to shore, but he cannot find Jim. He is taken in by the Grangerfords, a family engaged in a long-standing feud with another clan, the Shepherdsons. When one of the Grangerfords runs off to marry a Shepherdson, this old feud is rekindled. But seeing Buck's dead body is more than Huck can stand. He realizes how irrational and foolish feuding is, and he is frightened by the violence inherent in these two families who would kill one another because a member of one family has chosen to marry someone from the other family.
Not long after the shooting stops, Huck hears Jim call to him. Jim has been hiding because of the hunting dogs who could catch his scent and lead to his capture. Since Jim has repaired the raft, he and Huck decide to return to the river, they are free of society and its unfair rules. Huck comments, "Other places do seem so cramped up and smothery, but a raft don't. You feel mighty free and easy and comfortable on a raft....It's lovely to live on a raft"(Ch.18).
Huck begins to assess some of the faults in society, realizing that certain practices condoned by parts of society are immoral. Further examples of this moral corruption present themselves to Huck in the persons of the King and the Duke, ironically named by Twain to allude to the immorality of many monarchs. One morning near dawn, Huck sees two men who are apparently fleeing for their lives. Declaring that they have done no wrong and are trying to escape irrational men and their dogs, they beg Huck to save them. Huck tells them to hide and wade through the creek to throw off the dogs; then, he instructs them to move toward him on the river. When these men get on the raft, Huck notices their "big, fat ratty-looking carpet-bags." (Carpetbagger was a term used later during Reconstruction to refer to men from the North who came as opportunists to exploit people.)
These two “rapscallions” think nothing of exploiting people, whether that exploitation takes the form of a “little temperance revival” they charge people to attend or pretending to be a rich man’s relatives to steal children’s inheritances. When the Duke and the King attempt to pose as the brothers of a deceased, wealthy tanner named Peter Wilks, Huck feels he must act to prevent their crime. He finds the $6000 in gold that the two flim-flam men have stolen, and he hides it in Peter Wilks's coffin. Huck then informs one of Mr. Wilks's three daughters of the trickery that has been going on. This act is the first time that Huck has gone further than expressing disgust with the foolishness and wrongdoing he has witnessed. Huck has listened to the king and the duke as they "took on about that dead tanner like they'd lost the twelve disciples....It was enough to make a body ashamed of the human race"(Ch.24).
The climax of Huck's moral awakening and maturity comes with his determination to free Jim even though he may "go to hell." At one point, he has considered writing to Miss Watson and reporting Jim, but he does not. When he learns that the Duke and King stole Jim and sold him to a local farmer, Huck writes to Miss Watson. Somehow, Huck comments, Jim "couldn't seem to strike no places to harden me against him" (Ch.31). So Huck decides, "All right then I'll go to hell" (Ch.31) and tears up the letter. Then Tom Sawyer and Huck plan to free Jim. Unfortunately, Tom Sawyer gets shot in the leg during this endeavor, and Jim sacrifices his freedom to help Tom. Fortunately, however, Miss Watson, who has died, has freed Jim in her will.