Location Mapping

{
$schema: https://vega.github.io/schema/vega/v3.0.json
config: {
kibana: {
type: "map"
latitude: 37.0902
longitude: 95.7129
zoom: 4
}
}
data: [
{
"name": "cities",
"values": [
{"city": "Boston", "lon": 42.308126191, "lat": -71.07692974, "pop": 4823991},
{"city": "Boston", "lon": 42.34432328, "lat": -71.15778368, "pop": 2270800},
{"city": "Boston", "lon": 42.37525782, "lat": -71.02466343, "pop": 4485211},
{"city": "Boston", "lon": 42.32324363, "lat": -71.10892316, "pop": 397397},
{"city": "Adelaide", "lon": 42.28076737, "lat": -71.04736497, "pop": 1295714}
]
transform: [
{
type: geopoint
projection: projection
fields: ["lon", "lat"]
}
]
}
]
marks: [
{
type: symbol
from: {data: "cities"}
encode: {
enter: {
size: {value: 100}
fill: {value: "black"}
stroke: {value: "orange"}
}
update: {
x: {field: "x"}
y: {field: "y"}
}
}
}
]
}

I want to plot the map of US with Boston as the main city.