MacCready was born in 2265. He has served as the mayor of Little Lamplight for three years (since he was 10), when he was chosen by the other residents due to his smarts, toughness, and the fact that he doesn't take guff from anyone. He has no fear of adults and is a perfect representative. He is belligerent, small (even for his age), very distrustful of adults, and willing to blow someone's head off to defend his young charges, but MacCready is also very loyal to those he considers friends.
MacCready came into office in 2274 shortly after the five-minute rule of Princess. According to Sammy, when Princess demanded the title of Mayor to be changed to Princess, MacCready punched her in the nose and said that the children of Lamplight needed a leader, not a princess. He was then elected to the position of Mayor.
Picking Up the Trail/Rescue from Paradise: When first met, MacCready will threaten to shoot you unless you leave the Little Lamplight cavern entrance. The Lone Wanderer has to pass a difficult speech check, use the Child at Heart perk, or complete the Rescue from Paradise quest in order to gain entrance to Little Lamplight. After gaining entrance to Little Lamplight, the Lone Wanderer will have a new dialogue path with MacCready which reveals the entrance to Vault 87 through Murder Pass.
Fungus Deal: After speaking with either Eclair or Lucy, the Lone Wanderer can convince MacCready to enter a trade agreement: swapping either strange meat (to Eclair) or Buffout (to Lucy) for cave fungus.
Those!: The Lone Wanderer can convince MacCready (using the Child at Heart perk) to accept Bryan Wilks into Little Lamplight.
Speaking to MacCready in quick succession too many times will raise his ire. Eventually he'll refuse to talk to you and will tell you to leave Little Lamplight. Although you can still talk to him, you must wait 24 hours.
pc Mayor MacCready is prone to disappearing. He tends to wander into obscure and dark corners. He may appear near the front gate if you go outside and fast travel back to town, or standing on the platform where he first stood when he let you into town. You can move to his current position with the console command player.moveto 0000313b. [verified]
pc Sometimes MacCready will not give you the option to open the gate, even if you are at that point and have followed the advice outlined in this wiki. One way to make sure that this does not befall you is to click all of the grayed out speech options when speaking to MacCready. The dialog option to open the gate comes after a line that is often grayed/dimmed. [verified]
pc It's possible for MacCready to not open the gate after being instructed to do so. He will run to it, and climb up to the catwalk but will not activate the switch to raise the gate. This is because the scripted sequence requires Princess to be on the other end, and she may not run with MacCready to perform this function. Short of using the console to activate the gate/toggle clipping, the solutions are to: use the other entrance, reload from a previous save, or attempt to move Princess in range of the event with the console command prid 000185d5 followed by moveto player. [verified]
pc Doing DLC quests before opening the path will end "Picking Up the Trail" resulting in Macready's and Joseph's dialogue options to vanish and making entry into Vault 87 impossible. The only solution is to resort to a save that still has "Picking Up the Trail" as an active quest, and redo whatever progress has been lost. [verified]