The Role of Saltpeter in Frontierville
Farm animal manure trades in for saltpeter, which is used to make fireworks in Frontierville.
In Frontierville, you get loot drops for doing various tasks around your (or someone else's) homestead. Some types of loot always drop, for example coins, experience points, wood from wild trees, food from food trees or crops, or reputation hearts from working on neighbor homesteads. Others only drop some of the time. Feed a cow and you might get cheese. Chop at a pine tree and you might get a pine cone. Harvest some corn, maybe get cornbread. Each farm animal, crop, or wilderness clearing task comes with a collection set of five items - collect all five, and you can turn it in for a reward.
What Is Saltpeter?
In Frontierville, saltpeter is a collection reward for the manure collection. The collection includes piggy poop which drops from feeding pigs, poultry puddin' from chickens and geese, brush brownies from sheep and goats, meadow muffins from cows and oxen, and prairie pile from horses and mules. Of those, piggy poop and poultry puddin' drop often, while prairie pile is rare. It helps to feed as many of your neighbors' horses and mules as possible.
Once you've found at least one of each, the game will pop open a window congratulating you and asking if you want to trade it in. You can also find the completed collection by clicking on My Stuff (lower right button of the control panel, looks like a backpack), then Collections (lower right in the popup window, looks like a chest). Scroll through the pages until you find the manure collection. Click the green "Trade In" button at the upper right to get one saltpeter.
Saltpeter is used to make fireworks, which is an important step in Frontierville quests like the 4th of July Quest.
Fireworks and the 4th of July Quest on Frontierville
In the U.S. where Frontierville's game maker Zynga is based, July 4 is a holiday, Independence Day. It's a day that includes fireworks and family picnics. Part I of the 4th of July Quest is therefore to make five fireworks.
To make five fireworks, you will need one saltpeter plus five fire. Saltpeter comes from completing the manure collection. To make fire, click on your covered wagon and go inside. On your crafting workbench is an option to turn seven wood plus five cloth into one fire. Wood comes from chopping at wild trees, and cloth is often awarded when you visit neighbor homesteads.
Once you have enough fire and saltpeter, go inside your cabin. You make fireworks on the crafting workbench in there. After you're done, you'll advance to Part II of the quest - where you have to collect five cornbread (from corn), three hams (from pigs), and a ribeye (from oxen).
The 4th of July Quest is a limited-time quest that only happens in July (and so far only in 2010). However, there will no doubt be other limited-time quests that use fireworks, such as around New Years. Manure, saltpeter, and fireworks are available in Frontierville year-round.