Bottom-up instead of top-down

You wrote that

I gave them a general history of the planet, a specific history of the continent we started on and specific history of the starting town and surrounding areas.

It seems like you are using a top-down approach. I generally prefer bottom-up. Most people in a fantasy setting will not know anything about the planet or the continent they are living on. Most likely, those concepts will mean nothing to them, or maybe seem like theories for high-level mages or such that do not have any impact on their lives.

Start with only small bits of information on the immediate surroundings of the players, and give them more only if they ask for it, and if it makes sense in the settings that a character would know those things.

Players are interested in backstory if it gets them stuff

In my experience, feeding info dumps to the players is not a successful strategy, as they are usually concerned only with things that affect them and will ignore everything else.

That is, if the information you give them is not about enemies or opportunities for riches, it's often not deemed important. Therefore, try to weave in your information in a way that it relates to those things:

• The story of an abandoned tower should contain clues to safely overcome (some of) the traps and other dangers safeguarding the treasure.

• The story of a battle fought over the monastery a century ago can be told in the context of the holy avenger sword that was decisive in tipping the odds, but was lost afterwards.

• The story of the destruction of the sleepy farming town where the big bad grew up hints to his one true weakness.

Use 4e skill challenges to explore the story interactively

A great way to tell the story is to do it interactively - don't just tell it to them, but let them discover it in a skill challenge. Make sure that they can learn most of the important bits that you want them to learn without rolling, but enrich the story with information on major NPCs, details that give them leverage, or tactical information that they can use to their advantage.

Encourage player to contribute

In a comment, Brian S mentioned another important point - let the players contribute. Allow and encourage them to insert custom elements into the world and fill out blanks that catch their interest. One of the major strengths of pen and paper RPGs is the shared, collaborative approach to story-telling, and integration of player ideas can serve as a great motivator in addition to adding flavour to the world.

In my experience, actually hiding knowledge from all but one player is usually less dramatically interesting than the alternative. The reason is the concept of dramatic irony. Dramatic irony is when the audience of a story (in this case, you and the players) knows something that the characters do not. When you tell the whole table something that only one character knows, you now get to watch how that character explains the information in character, if they explain it at all. This is often hilarious, and just as often chilling. So most of the time, I think it's best just to tell the whole table and let them work it out in character.

That said, I think there are only two cases where you might want to pass notes, and they're rare enough that you can probably write the notes out before the session to save time:

1) When the character might have reason to keep the information to his/herself.

When Legolas sees riders in the distance, he's not going to not tell his friends about them. They're a team, and he's not a jerk. Hiding the information from other players and waiting for Legolas to convey it to them slows down the game and doesn't add anything meaningful to the experience. There are going to be very few situations where a character is going to want to hide information from the party. Mostly they come down to things like backstory, being secretly possessed by an evil wizard, or intra-party murder plots. If you're not running an evil campaign, this probably won't happen very often.

2) You don't trust your players not to meta-game.

This is the big one, and I think it's better to solve it by talking to players about roleplaying etiquette than by finding a way to pass them tons of secret notes. Make them understand that there is a difference between what they as players know, and what they as characters know. Even if they're A+ roleplayers, though, there will probably still be times when you want to avoid biasing their thinking. Maybe one character has been far away, scouting, and has some crucial information about an enemy attack, but you want the other characters to be standing around bickering with the emperor, completely oblivious, until the first character's breathless arrival.

Even in those cases, I find that a table full of good roleplayers is better able to help you tell a memorable story if the players have more information, rather than less. Basically, I'd say think very carefully about when a secret note would be helpful, write them all ahead of time, and stick to those instances only.