How to connect a Plotly Dash dropdown to a Choropleth map?

Question

I've been able to create Choropleth maps from the individual columns in this DataFrame. Here are the first five rows in my dataframe.

FIPS       Geographic Area        State  4/1/2010 Census  4/1/2020 Census  % Population Change  Unemployment Rate
0   22001                Acadia    LA            61787            57576            -6.815350                3.6
1   22003                 Allen    LA            25747            22750           -11.640191                4.0
2   22005             Ascension    LA           107215           126500            17.987222                2.9
3   22007            Assumption    LA            23416            21039           -10.151179                5.3
4   22009             Avoyelles    LA            42071            39693            -5.652350                3.7
5   22011            Beauregard    LA            35651            36549             2.518863                2.8

Here's the code I have so far.

"""Block of code I built to create the dataframe. I can create a Choropleth using Plotly without Dash using just the % Population  Change or the Unemployment Rate column. I want to use a Dash dropdown to change back and forth between the two"""

    df = pd.merge(df4, df5, on="Geographic Area", how='inner')

    app = dash.Dash()

    app.layout = html.Div([
        html.H2('Financial Genome Project'),
        dcc.Dropdown(
            id='census_type',
            options=[{"label": x, "value": x}
                     for x in df.columns[5:]],
            value=df.columns[0],
            clearable=False,
            style={'width': 300},
            placeholder="Select a census data type"
        ),
        html.Hr(),
        dcc.Graph(id="choropleth-chart"),
    ])

    @app.callback(
        Output("choropleth-chart", "figure"),
        [Input("census_type", "value")]
    )
    def display_choropleth(census_type):
        fig = px.choropleth(df, geojson=counties,
                            locations='FIPS',
                            color=census_type,
                            color_continuous_scale="rdylgn_r",
                            range_color=(0, 8),
                            scope="usa",
                            hover_name='Geographic Area',
                            # labels={'% Change': 'Population % Change'}
                            )

        # fig.update_layout(margin={"r": 0, "t": 0, "l": 0, "b": 0})
        fig.update_geos(fitbounds='locations', visible=False)
        return fig

    app.run_server(debug=True)


display_chart()

The dropdown works fine but it doesn't create a Choropleth map and I keep getting call back errors. See below.