diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 5ace460..700707c 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -1,6 +1,7 @@
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
 version: 2
 updates:
   - package-ecosystem: "github-actions"
-    directory: "/"
+    directory: "/" # Location of package manifests
     schedule:
       interval: "weekly"
diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
new file mode 100644
index 0000000..80859d3
--- /dev/null
+++ b/.github/workflows/CI.yml
@@ -0,0 +1,45 @@
+name: CI
+on:
+  push:
+    branches:
+      - main
+    tags: ['*']
+  pull_request:
+  workflow_dispatch:
+concurrency:
+  # Skip intermediate builds: always.
+  # Cancel intermediate builds: only if it is a pull request build.
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
+jobs:
+  test:
+    name: Julia ${{ matrix.version }} - ${{ matrix.os }} - ${{ matrix.arch }} - ${{ github.event_name }}
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 60
+    permissions: # needed to allow julia-actions/cache to proactively delete old caches that it has created
+      actions: write
+      contents: read
+    strategy:
+      fail-fast: false
+      matrix:
+        version:
+          - '1.10'
+          - '1.6'
+        os:
+          - ubuntu-latest
+        arch:
+          - x64
+    steps:
+      - uses: actions/checkout@v4
+      - uses: julia-actions/setup-julia@v1
+        with:
+          version: ${{ matrix.version }}
+          arch: ${{ matrix.arch }}
+      - uses: julia-actions/cache@v1
+      - uses: julia-actions/julia-buildpkg@v1
+      - uses: julia-actions/julia-runtest@v1
+      - uses: julia-actions/julia-processcoverage@v1
+      - uses: codecov/codecov-action@v4
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          fail_ci_if_error: true
diff --git a/.github/workflows/CompatHelper.yml b/.github/workflows/CompatHelper.yml
new file mode 100644
index 0000000..cba9134
--- /dev/null
+++ b/.github/workflows/CompatHelper.yml
@@ -0,0 +1,16 @@
+name: CompatHelper
+on:
+  schedule:
+    - cron: 0 0 * * *
+  workflow_dispatch:
+jobs:
+  CompatHelper:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Pkg.add("CompatHelper")
+        run: julia -e 'using Pkg; Pkg.add("CompatHelper")'
+      - name: CompatHelper.main()
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          COMPATHELPER_PRIV: ${{ secrets.DOCUMENTER_KEY }}
+        run: julia -e 'using CompatHelper; CompatHelper.main()'
diff --git a/.github/workflows/TagBot.yml b/.github/workflows/TagBot.yml
new file mode 100644
index 0000000..0cd3114
--- /dev/null
+++ b/.github/workflows/TagBot.yml
@@ -0,0 +1,31 @@
+name: TagBot
+on:
+  issue_comment:
+    types:
+      - created
+  workflow_dispatch:
+    inputs:
+      lookback:
+        default: "3"
+permissions:
+  actions: read
+  checks: read
+  contents: write
+  deployments: read
+  issues: read
+  discussions: read
+  packages: read
+  pages: read
+  pull-requests: read
+  repository-projects: read
+  security-events: read
+  statuses: read
+jobs:
+  TagBot:
+    if: github.event_name == 'workflow_dispatch' || github.actor == 'JuliaTagBot'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: JuliaRegistries/TagBot@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          ssh: ${{ secrets.DOCUMENTER_KEY }}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
deleted file mode 100644
index 2ffbad3..0000000
--- a/.github/workflows/ci.yml
+++ /dev/null
@@ -1,33 +0,0 @@
-name: CI
-
-on:
-  push:
-    branches: [ master ]
-  pull_request:
-    branches: [ master ]
-
-jobs:
-
-  test:
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        version: ['1', 'nightly']
-        arch: [x64, x86]
-        os: [ubuntu-latest, windows-latest, macOS-latest]
-        exclude:
-          # MacOS not available on x86
-          - os: macOS-latest
-            arch: x86
-    steps:
-      - uses: actions/checkout@v4
-      - uses: julia-actions/setup-julia@v1
-        with:
-          version: ${{ matrix.version }}
-          arch: ${{ matrix.arch }}
-      - uses: julia-actions/julia-buildpkg@v1
-      - uses: julia-actions/julia-runtest@v1
-      - uses: julia-actions/julia-processcoverage@v1
-      - uses: codecov/codecov-action@v3
-        with:
-          files: lcov.info
diff --git a/Project.toml b/Project.toml
index d3b9a52..c1678fe 100644
--- a/Project.toml
+++ b/Project.toml
@@ -3,5 +3,20 @@ uuid = "13e0c4e3-fd7a-51bf-9e22-ec7679f18909"
 authors = ["Daniel Matz <daniel.a.matz@nasa.gov>"]
 version = "0.2.0"
 
+[deps]
+Requires = "ae029012-a4dd-5104-9daa-d747884805df"
+
+[weakdeps]
+Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
+Requires = "ae029012-a4dd-5104-9daa-d747884805df"
+
+[extras]
+Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
+
+[extensions]
+UnitfulExt = ["Unitful"]
+
 [compat]
-julia = "1"
+Unitful = "1"
+julia = "1.2"
+Requires = "1"
diff --git a/README.md b/README.md
index b65bbd1..70efaa8 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ geometric altitude `z`, where `z` has units of m.
 
 The atmospheric state object that is returned has the following accessors:
 - `altitude`, which returns the altitude in m
-- `density`, which returns the density in units of kg/m²
+- `density`, which returns the density in units of kg/m³
 - `pressure`, which returns the pressure in units of Pa
 - `temperature`, which returns the temperature in units of K
 - `speed_of_sound`, which returns the speed of sound in units of m/s
diff --git a/ext/UnitfulExt.jl b/ext/UnitfulExt.jl
new file mode 100644
index 0000000..3286a3d
--- /dev/null
+++ b/ext/UnitfulExt.jl
@@ -0,0 +1,34 @@
+module UnitfulExt
+
+import COESA:
+    COESA,
+    atmosphere,
+    altitude,
+    mean_molecular_weight,
+    temperature,
+    pressure,
+    density,
+    speed_of_sound,
+    dynamic_viscosity
+
+isdefined(Base, :get_extension) ? (using Unitful) : (using ..Unitful)
+
+struct UnitfulState
+    state::COESA.State
+end
+
+altitude(s::UnitfulState) = altitude(s.state) * u"m"
+mean_molecular_weight(s::UnitfulState) = mean_molecular_weight(s.state) * u"kg/kmol"
+temperature(s::UnitfulState) = temperature(s.state) * u"K"
+pressure(s::UnitfulState) = pressure(s.state) * u"Pa"
+density(s::UnitfulState) = density(s.state) * u"kg/m^3"
+speed_of_sound(s::UnitfulState) = speed_of_sound(s.state) * u"m/s"
+dynamic_viscosity(s::UnitfulState) = dynamic_viscosity(s.state) * u"N*s/m^2"
+
+function atmosphere(Z::Quantity)
+    Z′ = ustrip(u"m", Z)
+    state = atmosphere(Z′)
+    UnitfulState(state)
+end
+
+end
diff --git a/src/COESA.jl b/src/COESA.jl
index 98c59bb..39c115f 100644
--- a/src/COESA.jl
+++ b/src/COESA.jl
@@ -1,5 +1,16 @@
 module COESA
 
+# Support package extensions on Julia < 1.9
+if !isdefined(Base, :get_extension)
+    using Requires
+end
+
+@static if !isdefined(Base, :get_extension)
+    function __init__()
+        @require Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d" include("../ext/UnitfulExt.jl")
+    end
+end
+
 export
     atmosphere,
     altitude,
diff --git a/test/Project.toml b/test/Project.toml
index 737dfda..1368296 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -2,3 +2,4 @@
 Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
 JET = "c3a54625-cd67-489e-a8e7-0a5a0ff4e31b"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
diff --git a/test/runtests.jl b/test/runtests.jl
index 67b8c62..c4bcbfe 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,7 +1,10 @@
 using COESA
 using Test
-using Aqua
-using JET
+import Aqua
+import JET
+using Unitful
+
+quantity_type(T, units) = Quantity{T, dimension(units), typeof(units)}
 
 M0 = COESA.M0
 
@@ -239,12 +242,26 @@ M0 = COESA.M0
         @test_throws ErrorException dynamic_viscosity(atmos)
     end
 
+    @testset "Unitful Extension" begin
+        atmos = atmosphere(0u"m")
+        @test altitude(atmos) == 0u"m"
+        @test round(quantity_type(Float64, u"kg/kmol"), mean_molecular_weight(atmos), sigdigits = 5) == 28.964u"kg/kmol"
+        @test round(quantity_type(Float64, u"K"), temperature(atmos), sigdigits = 6) == 288.150u"K"
+        @test round(quantity_type(Float64, u"Pa"), pressure(atmos), sigdigits = 6) == 101325u"Pa"
+        @test round(quantity_type(Float64, u"kg/m^3"), density(atmos), sigdigits = 5) == 1.2250u"kg/m^3"
+        @test round(quantity_type(Float64, u"m/s"), speed_of_sound(atmos), sigdigits = 5) == 340.29u"m/s"
+        @test round(quantity_type(Float64, u"N*s/m^2"), dynamic_viscosity(atmos), sigdigits = 5) == 1.7894e-5u"N*s/m^2"
+    end
+
     @testset "Code Quality" begin
         @testset "Aqua" begin
-            Aqua.test_all(COESA, project_extras = false)
+            Aqua.test_all(COESA)
         end
         @testset "JET" begin
-            test_package("COESA")
+            # JET doesn't export `test_package` for older versions
+            if isdefined(JET, :test_package)
+                JET.test_package("COESA")
+            end
         end
     end